Pemphigus Vulgaris

Abstract

Pemphigus vulgaris is a life-threatening bullous disease characterized by acantholysis resulting in the formation of intraepithelial blebs in the mucous membranes and skin. It is a chronic autoimmune bullous dermatosis caused by the production of autoantibodies against desmoglein 1 and 3. It often begins with blisters and erosions on the oral mucosa, followed by lesions on other mucous membranes and drooping blisters that may spread to the skin. If there is clinical suspicion, the diagnosis can be confirmed by cytological examination, histopathological examination, direct and indirect immunofluorescence tests. Before the introduction of corticosteroids, PV was fatal due to dehydration or secondary systemic infections. The mainstay of treatment is still systemic steroids. Immunosuppressants such as azathioprine, mycophenolate mofetil and methotrexate, high-dose intravenous immunoglobulins, CD20 monoclonal antibody Rituximab treatments are used as an adjuvant with steroids in suitable patients and successful results are obtained.

1. Introduction

Pemphigus vulgaris (PV) is a rare disease that causes blisters. It is the most common type of pemphigus group disease. The name of pemphigus derives from the Greek word ‘pemphix’. It is a disease characterized by intraepidermal bullae of skin and mucosa that can be life-threatening.

2. Epidemiology

The incidence of pemphigus group disease is about 1 in 100,000, while PV occurs at a rate of 0.1 to 0.5 per 100,000, with a higher rate in Ashkenazi Jews and people of Mediterranean descent. In India, Malaysia, China and the Middle East, PV accounts for 70% of all pemphigus cases and is the most common autoimmune bullous disease [1].

The average age of onset is between 45- and 65 years. Pemphigus is rare under 18 years of age, except in endemic areas where 30% of patients are reported to be younger than 20 years of age [2]. All over the world, men and women are equally affected. However, adolescent girls are more affected than boys of the same age [3].

3. Predisposing factors

PV is a polygenic disease and low titers of disease-associated autoantibodies have been demonstrated in first-degree healthy relatives of patients with pemphigus [4, 5]. For many years, a strong association between Class II Human leukocyte antigen (HLA) polymorphism and pemphigus vulgaris has been known, with the highest incidence seen among Ashkenazi Jews. The interethnic variability in the occurrence of pemphigus vulgaris has been associated with genetic susceptibility. Associated HLA polymorphisms are HLA-DRB1∗ 0402, HLA-DRB1∗14, HLA-DQB1∗ 0503, HLA-DRB1∗ 0302 and HLA-DRB1∗ 08. Of these, HLA-DRB1∗ 0402, HLA-DRB1∗ 14 and HLA-DRB1∗ 08 have a statistically significant relationship with the incidence of pemphigus vulgaris [6].

Pemphigus vulgaris is associated with a variety of diseases, including other autoimmune disorders, psoriasis, neurological and psychiatric disorders, and some malignancies [7]. In addition, environmental factors may also be effective in initiating and maintaining the disease process. These causes include medications, viral infections, physical agents, contact allergens, vaccines, diet and psychological factors (Table 1) [8, 9, 10, 11].

Drugs	Containing a Thiol Group	Penicillamine, Captopril, and Cephalosporin
	Containing a Phenol Group	Cephalosporin,; Rifampin, and Levodopa
	Other	ACE inhibitors other than captopril, most NSAIDs, biological modifiers of the immune response (vaccine, interferons, imiquimod and other cytokines), chloroquine/hydroxychloroquine, cocaine
Viral İnfections	HSV, HHV8, and EBV
Physical Agents	Sunburns, ionizing radiation, thermal or electrical burns, and surgical and cosmetic procedures
Contact Allergens	Chemical exposure in those involved in photography, dry cleaning, industrial solvent work, horticulture, pesticides and intensive agriculture
Dietary Factors	Although not proven, thiol allyl compounds in garlic, leeks and onions, as well as tannins in black pepper, red pepper, cherry, cranberry, blackberry, red wine and tea are known to cause acantholysis

Table 1.

Trigger factors for pemphigus vulgaris.

4. Pathogenesis

Pemphigus vulgaris is an autoimmune condition that is more likely to develop in patients with certain HLA types after triggers. Central to the pathogenesis of pemphigus is the presence of immunoglobulin (Ig) antibodies against proteins on the cell surface of keratinocytes. Immunochemical and molecular cloning studies have shown that antigenic targets in PV are desmogleins. Desmogleins (Dsg) are desmosome-associated transmembrane glycoproteins that provide cell-cell adhesion in the epidermis [3]. The main antigen in PV is Dsg3 (130 kDa), but 50% of patients also have autoantibodies against Dsg1 (160 kDa). The ratio of Dsg1 and Dsg3 antibodies appear to correlate with the clinical severity of PV; those with only Dsg3 antibodies have predominantly oral lesions. IgG antibodies against Dsgs impair the adhesive function of desmosomes and inhibit cell-cell adhesion. This results in epidermal acantholysis and drooping blister formation, which is the characteristic clinical feature of pemphigus diseases [3].

The localization of blister formation and involvement of mucosal surfaces varies with the pemphigus disease subtype and can be explained by the Dsg compensation theory. This theory states that on cutaneous surfaces, Dsg 1 is expressed in all layers of the epidermis, while Dsg 3 is expressed in deeper layers. Dsg 1 expression in the mucosa is minimal, while Dsg 3 is dominant. The interpretation of the Dsg compensation theory, as it relates to the clinical manifestations in pemphigus, can be summarized as follows: Only patients with antibodies to Dsg 3 should have mucosal dominant PV because Dsg 1 compensates for the loss of Dsg 3 in the skin. Mucous membranes predominantly contain Dsg 3; low levels of Dsg 1 in the mucosa cannot replace the lost Dsg 3 and lead to epithelial acantholysis and mucosal erosions. When antibodies against both Dsg 1 and 3 develop, epidermal acantholysis occurs in both the skin and mucous membranes. It is still a matter of debate whether the Dsg compensation theory can adequately explain the complex pathogenic mechanism of pemphigus [3, 12].

Although Dsgs are the main autoantigens targeted by autoantibodies in the vast majority of pemphigus patients, antibodies against other desmosomal cadherins (e.g., desmocollins), desmoplakin and acetylcholine receptors on keratinocytes have also been detected in patients with pemphigus vulgaris [13, 14]. In recent years, the blood of some PV patients has been found to show reactivity with Dsg4, which has similar properties to Dsg1 and Dsg3, but the pathogenic nature of anti-Dsg4 is unclear [14]. In the presence of both anti-Dsg 1 and anti-Dsg 3 antibodies in PV, the entire skin should have been completely lysed. However, such a clinic is not seen in any patient. Therefore, the separation of keratinocytes may also be due to a different subset of non-Dsg pemphigus antibodies that recognize and block keratinocyte acetylcholine receptors. In this light, the earliest sign of keratinocyte separation is maintained by autoantibodies to these acetylcholine receptors located on the keratinocyte membrane, while antiDsg antibodies will only then be activated, triggering cell-cell separation [8]. Pharmacological blockade of acetylcholine receptors with muscarinic or nicotinic antagonists, atropine and mecamylamine, respectively, resulted in pemphigus-like acantholysis in monolayers of human oral and epidermal keratinocytes in both conditions. These observations suggest that PV IgGs act antagonistically to acetylcholine receptors of keratinocytes, interrupting the stimulation of these receptors by acetylcholine, thereby, altering the normal pattern of keratinocyte adhesion via cholinergic signaling that can lead to acantholysis [15].

Caspases are involved in the pathogenesis of PV through apoptosis and acantholysis. Caspases are activated through various cellular pathways to affect programmed cell death. While apoptosis via caspases is a normal process in the body, the presence of PV-IgG causes pathological activation of caspases in keratinocytes. In all studies, inhibition of caspases has been shown to reduce apoptosis and acantholysis and thus have a positive effect on cell-cell adhesion [16].

The pathogenesis of pemphigus involves the production of activated B-cells and IgG with stimulation by IL-4 by T-helper 2 (Th2) cells. Excessive activation of Th2 cells causes the production of autoantibodies required for PV. Th2 cells secrete IL-4 and multiple interleukins (IL), which are known to play an important role in pemphigus. IL-4 promotes antibody production by primed B cells and an isotype switching from IgG1 to IgG4 antibodies which are important in the active form of PV. IL-4 also causes naive CD4+ T cells to differentiate into Th2 cells, thus maintaining the disease. Production of autoantibodies and epitope binding are sufficient for the loss of adhesions directly between desmosomes [17].

Intracellular kinase signaling has been identified in the pathogenic process of PV. Intracellular kinase signaling has been identified in the pathogenic process of PV. The binding of autoantibodies in PV promotes phosphorylation of kinases. In the study in which patients with a diagnosis of PV were examined, kinases (e.g., phosphokinase C (PKC), p38 mitogen-activated protein kinase (p38MAPK), cyclin-dependent kinase (Cdk2), sarcoma-associated kinase (Src), extracellular signal-regulated kinase (ERK), Bruton tyrosine kinase (BTK), apoptosis signal regulatory kinase (ASK1), epidermal growth factor receptor kinase (EFGRK)), tyrosine kinase (TK)) were found to be phosphorylated in PV-induced models [16]. Inhibition of these pathways reduces acantholysis in vitro and in vivo. The role of p38MAPK has been highlighted in multiple studies. p38MAPK is activated after PVIgG-binding upstream of Rho kinase. In particular, p38MAPK inhibition prevents PV-IgG–induced redistribution of Dsg3 and results in PV-IgG and Dsg3 co-localizing at the cell membrane. As a result, p38MAPK inhibition has been shown to prevent both histologic and clinical blister formation in both in vivo and in vitro models. Therefore, p38MAPK plays an essential role in regulating Dsg3 internalization and must be considered as a key component in PV pathogenicity [16].

Proteases are enzymes that hydrolyze peptide bonds within proteins. Proteases have been blamed because the use of various protease inhibitors was found to be effective in inhibiting PV-associated acantholysis in studies [16]. Pemphigus antibodies (described as IgGp) may mediate acantholysis by the activation and release of non-lysosomal proteolytic enzymes from epidermal cells. Recent data indicate that the proteolytic enzyme is an activator of plasminogen. This has been demonstrated by the addition of a plasmin inhibitor such as aprotinin, which can inhibit the development of acantholysis when PV or PF IgG is added to the skin in organ cultures. Both plasminogen and IgG are required to cause acantholysis [15].

There are many mechanisms in the pathogenesis of PV that are still not understood and more studies are needed.

5. Comorbidities

In cross-sectional studies, pemphigus is associated with some diseases including psoriasis, hematological and solid organ malignancies (esophageal and laryngeal cancer), other autoimmune diseases (Sjögren’s syndrome, systemic lupus erythematosus and alopecia areata), and neurological diseases (dementia, Parkinson’s disease and epilepsy), Crohn disease and ulcerative colitis. Studies on the comorbidities of PV are needed.

6. Clinical features

All patients with PV develop painful erosions of the mucosal areas, especially oral mucosa. Oral lesions are the first finding in 50–70% of cases and occur during the course of the disease in 90% of patients [18]. More than half of patients also develop flaccid blisters and extensive cutaneous erosions. PV is divided into two subgroups according to the area of involvement: (1) mucosal dominant type, in which mucosal erosions are prominent and skin involvement is minimal; and (2) mucocutaneous type with extensive cutaneous bullae and erosions in addition to mucosal involvement [19].

Mucosal erosions usually precede the cutaneous manifestations of the disease. In some cases, oral ulcers may be the only manifestation of the disease. Intact bullae are rare because they are fragile and break easily. Although diffuse or widespread erosions can occur anywhere in the oral cavity, the most common sites are the buccal and palatine mucosa, lips and gingiva. Erosions are numerous and found in varying sizes and irregular shapes; they extend peripherally and there is usually a delay in re-epithelialization. Gingival involvement is seen as desquamative gingivitis. There are fissured hemorrhagic crusts that can extend up to the vermilion border in lip involvement. Involvement of the oral mucosa may impair nutrition and therefore the general condition of the patient [20]. Lesions of the nasal mucosa lead to hemorrhagic crusts. Apart from the oral and nasal mucosa, the oropharynx, esophagus, conjunctiva, larynx, urethra, vulva, vagina, penis and anus are other mucosal involvement areas.

Skin involvement may be localized or generalized. Often there are clear flaccid blisters on normal or erythematous skin. The contents of the bullae are clear at first, but over time they may become turbid, seropurulent and hemorrhagic. The bullae may coalesce and rupture quickly to form painful erosions that bleed easily. Erosions are covered with crusts that heal slowly in a short time. PV skin lesions can be seen anywhere on the body, but the involvement of the trunk, groin, axilla, scalp and face is common, while the palms and soles of the feet are usually protected.

Due to the abundance of Dsgs in the hair follicles, the scalp is a unique place for pemphigus. In the course of pemphigus, scalp involvement is observed in up to 60% of patients. Erosions, crusts and scaly plaques can sometimes lead to alopecia. Effortless removal of anagen hairs in a pull test is a sign of high disease activity [21].

The flaccid nature of the blisters seen in PV are due to intraepidermal acantholysis caused by anti-Dsg antibodies. Due to the loss of cohesion in the epidermis, it moves easily laterally in patients with active disease (Nikolsky sign) by applying light pressure or friction to the upper layers of the skin [19]. Direct Nikolsky (Asboe–Hansen sign) is the spreading of the blister to adjacent skin by applying light pressure on a blister, indirect Nikolsky is the application of rubbing to clinically normal-appearing skin to cause separation as a result of rubbing. These findings are not 100% specific for the diagnosis, but their presence suggests PV. These signs clinically represent acantholysis or loss of cell adhesion. It can also be found in other forms of pemphigus, as well as in toxic epidermal necrolysis [19, 20].

Pruritus is rare. Both mucosal and skin lesions heal without scarring, but hyperpigmentation in the affected areas may persist for months, especially in dark-skinned patients. PV is a chronic disease with periods of remission and exacerbation. Without appropriate treatment, PV can be fatal because extensive skin involvement may result in loss of epidermal barrier function and lead to loss of body fluids, malnutrition, and secondary infections. Secondary bacterial infection is one of the most common complications and can progress to septic shock [19, 20].

Among the rare clinical findings of PV; isolated crusty plaques on the face and scalp, foot ulcers, dyshidrotic eczema, macroglossia, nail dystrophy, paronychia and subungual hematomas can be counted. Nail involvement usually occurs when the disease is severe and in most cases responds partially or completely to systemic therapy [1, 19]. In the literature, two patients with cervical pemphigus vulgaris with symptoms as postmenopausal bleeding have been reported [22].

7. Disease activity assessment

Various scoring systems have been developed and validated for assessing pemphigus disease severity. The most widely used disease activity scoring system is the Pemphigus Disease Activity Index (PDAI). PDAI is based on the number of lesions found in the skin, scalp, and mucosa and the area of skin lesion. PDAI is an objective scoring method as it gives equal weight to the involvement of the skin and different mucosal areas and provides extra evaluation within the scalp. In addition, the fact that it consists of a single-page form provides ease of use. This score ranges from 0 to 263, moderate disease is defined by a PDAI score of 14 or less, major disease is defined by a PDAI score of 15 to 44, and extensive disease is defined by a PDAI score of 45 or higher [7, 23]. Another frequently used scoring method is ABSIS (Autoimmune Bullous Skin Disorder Intensity Score). It is evaluated between 0 and 206 according to the clinical severity of skin lesions, the number of areas involved in the oral mucosa, and the discomfort during feeding. When evaluating this score, ABSIS <17 is considered a mild disease, ABSIS 17–53 is considered a moderate disease, and ABSIS >53 is considered a severe disease. The advantages of this method are that it allows both objective and subjective evaluation and can be used in all bullous diseases [7, 23]. A third system, called the Pemphigus Vulgaris Activity Score (PVAS), takes into account the localization, morphology and severity of mucocutaneous lesions, as well as the presence of Nikolsky’s sign [24].

8. Diagnosis

Early and accurate diagnosis is important. This is dependent on the co-detection of clinical presentation and tissue-bound and/or circulating autoantibodies.

The diagnosis of pemphigus vulgaris begins with a thorough history and physical examination. Since the presence of mucosal lesions is more common in PV than in other pemphigus, it should detect the presence of mucosal involvement. Mucosal involvement may not always be in the areas to be seen during the examination. Therefore, clinicians should question the presence of ocular symptoms, hoarseness, dysphagia and dyspareunia to assess the involvement of all mucosal surfaces [3]. Drug use should be questioned.

After a thorough history and physical examination, two separate biopsies should be obtained from the patient for both histopathological examination and DIF.

A 4 mm punch biopsy should be taken from the edge of the early lesion or erosion for hematoxylin and eosin (H&E) staining and routine histopathological examination. For direct immunofluorescence (DIF), an additional perilesional skin biopsy should be taken from normal-appearing skin 4 mm from a vesicle or erosion. Lesions of skin biopsies for DIF are more likely to be associated with false-negative results as a result of the elimination of immunoreactions involved in the inflammatory process of the underlying pemphigus disease. DIF biopsies should not be placed in formalin. Michel medium or Zeus medium should be used. Fresh specimens also may be sent to the laboratory, provided they are kept moist with saline and processing within 24 hours.

The characteristic histopathological finding in PV is acantholysis due to loss of intercellular adhesion without necrosis in keratinocytes and thus the formation of intraepidermal bullae. Although acantholysis is often located just above the basal layer (suprabasal), intraepidermal localization at the level of the stratum spinosum has also been reported to a lesser extent. There are epidermal cell clumps and acantholytic cells in the bulla cavity. Although basal keratinocytes lose their connection with the adjacent cell, they do not lose their bond with the basal membrane through hemidesmosomes, leading to the appearance of a ‘tombstone pattern’ [19]. Sparse inflammatory infiltrates in the dermis with eosinophils.

The gold standard in the diagnosis of PV is direct immunofluorescence (DIF) microscopy, which can detect tissue-bound autoantibodies [4]. In DIF, there is the accumulation of IgG and C3 in the intercellular space throughout the mid-lower or entire epidermis.

IIF and ELISA are serological tests that detect circulating autoantibodies that bind epithelial cell surface antigens. These tests are used to further support the diagnosis of pemphigus in patients with a positive DIF result. More than 80% of pemphigus vulgaris patients have circulating antibodies detectable by IIF. The substrate used affects the test sensitivity [25]. The monkey esophagus is the preferred substrate for the diagnosis of pemphigus vulgaris. Intercellular ‘honeycomb’ or ‘coil wire’ IgG accumulation is observed in PV [26]. The enzyme-linked immunosorbent assay (ELISA) test can be used for IgG antibodies to Dsg 1 and Dsg 3. ELISA is more sensitive and specific than IIF in the diagnosis of pemphigus vulgaris [25]. The ELISA test can also be used to monitor disease course and response to therapy in PV. In a study in which Dsg 1 and Dsg 3 autoantibody levels were followed in patients under treatment, it was found that Dsg 1 level more clearly showed the course of the disease. Dsg 3 antibody levels remained elevated during remission in some patients with mucosal pemphigus vulgaris [27]. Antibodies can be detected in patients who do not yet have clinical signs of pemphigus and can be found in patients with staphylococcal scalded skin, penicillin adverse drug reactions, toxic epidermolysis necrosis and burns [1].

Additional serological tests that may be used to diagnose pemphigus vulgaris include immunoblotting and immunoprecipitation. However, these tests are more difficult to perform than IIF and ELISA. Therefore, they are rarely used in the clinical setting.

In addition, cytological examination (Tzanck smear) stained with hematoxylin and eosin is useful for rapid demonstration of acantholytic keratinocytes of the spinous layer (abundant eosinophilic cytoplasm and rounded central nucleus) [20].

9. Differential diagnosis

Diagnosis is more difficult in patients with only oral lesions. Differential diagnoses for mucosal lesions include stomatitis secondary to herpes simplex virüs, aphthous ulcers, lichen planus, erythema multiforme, Stevens-Johnson syndrome, paraneoplastic pemphigus cicatricial pemphigoid, autoimmune diseases such as systemic lupus erythematosus or dermatitis herpetiformis [1, 19]. The differential diagnosis of cutaneous lesions includes other forms of pemphigus, bullous pemphigoid, linear Ig A bullous dermatosis, erythema multiforme, Hailey-Hailey disease and Grover’s disease, epidermolysis bullosa acquisita [1, 19]. Demonstration of IgG autoantibodies against keratinocyte cell surfaces and anti-Dsg3 IgG will exclude these diseases (except drug-induced pemphigus vulgaris and paraneoplastic pemphigus). Fresh bullous pemphigoid blisters are tense due to a subepidermal division. The Hailey-Hailey disease has full-thickness acantholysis ‘dilapidated brick wall’ with epidermal hyperplasia and impetiginized scales, and acantholysis does not extend follicles down as in pemphigus. Transient acantholytic dermatosis exhibits only small intraepidermal foci of acantholysis [1].

10. Treatment

Prior to the use of systemic corticosteroids, pemphigus vulgaris was an often fatal disease. Most patients would die within 2–5 years from the onset of the disease. Extensive involvement of the body surface led to the loss of epidermal barrier function and increased fluid loss or secondary bacterial infections. The anti-inflammatory effects of corticosteroids have made them one of the most important drugs in the treatment of autoimmune bullae diseases, and their use has reduced the mortality rate by 60%. Without treatment, PV has a mortality rate ranging from 60 to 90% [28]. However, these agents are not without their side effects, and the mortality of PV remains significant (5–20%), largely due to complications of long-term immunosuppression. However, immunosuppressive agents remain important in the treatment of PV [29].

The first line of treatment is corticosteroids. Recommends starting prednisone treatment at doses of 0.5–1.5 mg/kg/day (mean 1 mg/kg/day, 60 mg/day) for approximately 2 weeks or more. If disease control is not achieved thereafter, the dose is increased to 2 mg/kg/day or reduced to 25% per week unless relapsed [29]. Pulse therapy in the form of 1 gr/day can also be used (with close cardiological monitoring), but it is not recommended due to the high risk of side effects.

The following should be considered when deciding which immunosuppressive drug to use in the patient. First, the patient’s medical condition, general health, comorbidities, and the response of PV to corticosteroid therapy. Second, the level of steroid-sparing effect required to maintain clinical remission if the disease is under control. Third, data on remission times, the incidence of relapse, and time to relapse [29].

Adjuvant Therapies; azathioprine (AZA) is a cytotoxic drug used in many autoimmune diseases. It is the oldest and most prescribed immunosuppressive drug used for PV, and contributes to treatment by suppressing lymphocyte proliferation and antibody synthesis. AZA is an effective adjunctive immunosuppressive agent for pemphigus, with clinical remission rates of approximately 50% in retrospective studies [25]. The recommended dose of AZA in PV is 1 to 3 mg/kg/day orally in two divided doses. It should be used for four to six weeks to achieve a full therapeutic effect, which limits its use as monotherapy. In case of unsatisfactory clinical response, it is recommended to continue use for 3 months before replacing with another adjuvant [20]. Due to genetic polymorphisms that affect AZA clearance and activation, testing for thiopurine methyltransferase (TPMT) levels is strongly recommended prior to initiating therapy. In general, adults with pemphigus with high TPMT activity should be treated with a normal dose of AZA (up to 2.5 mg/kg/day), and those with moderate or low TPMT activity at a low maintenance dose (up to 0.5–1.5 mg/kg/day) should be treated with AZA therapy, should not be given to patients without TPMT activity [26]. Blood and liver enzymes should be monitored weekly for the first month of treatment and biweekly after the second month. Intervals can be increased later. Serious side effects include reversible lymphopenia, neutropenia and early pancreatitis. More commonly, gastrointestinal upset and hepatotoxicity, which can be reduced by dose adjustment, have been reported [29].

Mycophenolate mofetil (MMF) has been used as an adjuvant to corticosteroids in patients who do not respond to AZA. Several groups prefer MMF to AZA as first-line adjuvant therapy in PV because of its low hepatotoxicity and comparable efficacy. It is started at a dose of 2–3 g/day divided into two doses in combination with MMF systemic steroid. This combination therapy has been shown to provide clinical remission in an average of 9 months. Therapeutic failure should only be considered after 3 months of use at a dose of 3 g/day. Its main side effects are altered bowel habits, neutropenia, lymphopenia and myalgia. Its use is contraindicated in case of hematological dysfunction, acute and chronic infections, pregnancy and malignancy. Because it is teratogenic, contraception should be initiated in women of childbearing age before starting MMF therapy. Complete blood count and liver-kidney function tests should be performed at the start of treatment, every other week for the first 3 months, and monthly after 3 months of treatment. In addition, patients should be followed up for the development of cutaneous neoplasms and lymphoma.

Although not as frequently used as AZA or MMF, it is an alternative to methotrexate (MTX) for immunosuppressive therapy in pemphigus vulgaris. In a retrospective study of 30 PV patients treated with adjuvant methotrexate at a dose of 15 mg per week, it was shown that 84% of patients showed clinical improvement within 6 months and the steroid dose could be reduced in 21 (76.6%) and MTX was effective and safe in the treatment of PV has been reported [30]. Before starting treatment, complete blood count, liver and kidney function tests and urinalysis should be performed. It is then recommended to monitor the blood count and liver function tests once a week for the first month, monthly for the next 2 months, and then every 2–3 months. Major side effects are susceptibility to infections and liver dysfunction. Hepatotoxicity is important during drug use. In some studies, it has been stated that if the patient is not in the risk group for liver disease, liver biopsy may not be performed by monitoring the procollagen III level [29]. Side effects can be alleviated with the administration of 5–10 mg of folic acid after methotrexate treatment.

Cyclosporine is a selective inhibitor of calcineurin and acts by reducing the transcription of cytokines required for T-lymphocyte proliferation. This may suppress the autoimmune response in the pathogenesis of PV [29]. Some authors report that the efficacy of cyclosporine in the treatment of pemphigus is limited compared to AZA or MMF [31]. The standard dose is 2.5–3 mg/kg/day. Cyclosporine requires close monitoring for hypertension and renal toxicity.

Cyclophosphamide, as an alkylating agent, cross-links DNA and suppresses B and T lymphocyte responses, thereby helping PV treatment by reducing antibody production [29]. Cyclophosphamide is administered at a dose of 1–3 mg/kg/day (usually 50–200 mg/day). The most important side effects are hemorrhagic cystitis, infertility and leukopenia. Complete remission was achieved in 17 of 20 patients with PV, and treatment failed in three patients. The treatment was applied for an average of 17 months and the patients were followed for 27 months. The median time to complete remission was reported as 8.5 months. Hematuria was observed in five patients, mild infection in six patients, and transitional cell carcinoma of the bladder 15 years later in one patient. There were no deaths due to cyclophosphamide treatment [32]. In another study, weekly intravenous cyclophosphamide infusion with high-dose corticosteroids safely, effectively and quickly controlled the condition of corticosteroid-insensitive patients with resistant PV, shortened hospital stay and prevented the risk of further complications [33]. Several small case series have evaluated regimens of immunoablative intravenous cyclophosphamide with daily oral therapy (1.1–2.5 mg/kg/day), intermittent high-dose intravenous dexamethasone and cyclophosphamide with 50 mg/day oral cyclophosphamide daily. Although none of them are curative, all methods have been found to be effective in the short term. Significant adverse events, including hematuria, infection and transitional cell carcinoma of the bladder, have been observed with high-dose treatment regimens. In a study using low-dose cyclophosphamide (1.0–1.5 mg/kg/day), no significant difference in the safety profile was observed when compared with other immunosuppressive agents. With the risk of infertility, cyclophosphamide is not considered a first-line steroid-sparing agent in the treatment of PV [25].

Dapsone inhibits various inflammatory mediators, but its exact mechanism of action in PV is unknown [34]. Steroid-reducing effects have been demonstrated at doses up to 100 mg/day or ≤ 1.5 mg/kg/day [35]. In different studies, Dapsone showed a trend toward efficacy as a steroid-sparing drug in PV, but the results were not statistically significant. It can be used with other immunosuppressants, especially Rituximab. It helps in the prophylaxis of Pneumocystis pneumonia [25]. Serum glucose-6-phosphate-dehydrogenase (G6PDH) activity should be checked before starting treatment.

Plasmapheresis, the process typically involves plasma exchange to remove IgG antibodies from the serum and replace them with albumin, fresh frozen plasma, or donor plasma. Plasmapheresis is sometimes used to treat severe pemphigus or PV unresponsive to a combination of corticosteroids and immunosuppressive agents. Although one controlled study reported ineffectiveness, other studies have shown that both reduces serum autoantibody levels and controls disease activity [25]. For maximum efficacy, patients should receive immunosuppressive agents to avoid the antibody rebound phenomenon that may follow IgG removal, the most commonly used agent for this purpose is Cyclophosphamide [25, 29]. Side effects of plasmapheresis include sepsis, hypotension and depletion of clotting factors.

Immunoadsorption (IA) is an advanced technique used to remove circulating antibodies in patients with severe disease and high IgG titers. Removal of pathogenic antibodies from the circulation has been theorized to promote the migration of anti-Dsg3 antibodies from the skin to the systemic circulation, thereby minimizing autoantibody binding to antigens in the epidermis, thereby preventing the underlying pathogenesis of pemphigus. Cost and availability are major limiting factors for the use of IA [29]. The basic principles of IA are actually similar to plasmapheresis, but when the two are compared, IA does not remove plasma proteins such as albumin and clotting factors. The use of plasmapheresis in pemphigus has been largely abandoned due to the significant incidence of serious adverse events such as sepsis [36].

Pulse Corticosteroid, intravenous, pulsed administration of 250 to 1000 mg of methylprednisolone administered over approximately 3 hours per day for 4 to 5 consecutive days can achieve prolonged remission and reduce the total dose of glucocorticoids needed to control the disease. Although the goal of this therapy is to reduce the incidence of complications from long-term steroid use, it can cause cardiac arrhythmias resulting in sudden death, in addition to all the usual glucocorticoid complications, and its use remains controversial. In addition, a controlled trial showed that adjuvant oral dexamethasone pulse was not superior to standard treatment with prednisolone and AZA for PV. Simply giving lower doses of prednisone in divided doses may produce the same result with fewer side effects [25].

Rituximab; chimeric monoclonal anti-CD 20 antibodies. Rituximab binding to CD20 induces B-cell depletion by, at least, four different mechanisms:

1. Direct induction of programmed cell death, which is dependent on activation of caspases and involves intracellular molecules, including Src kinases, p38 MAPK and NFkB.

2. Complement-dependent cytotoxicity, which happens when C1s binds to Rituximab opsonized cells and trigger complement activation and formation of the membrane attack complex (MAC), which eventually induces cell lysis.

3. Antibody-dependent cytotoxicity, which consists of activation of NK cells through binding the human Fc portion of Rituximab to the FcRIII receptor: this activates NK cells to release cytotoxic mediators, including perforins and granzyme B, which induces caspases-dependent cell death in the target lymphocyte.

4. Antibody-dependent phagocytosis, in which neutrophils, monocytes and macrophages bind Rituximab opsonized B-cells through the Fcγ Receptor. Recently, a new mechanism referred to as trogocytosis, or shaving has been characterized. In trogocytosis, macrophages remove Rituximab-CD20 complexes by transferring plasma membrane; this triggers cell death through a yet-to-be identified mechanism [36].

Despite being used in the treatment of pemphigus since the early 2000s, anti-CD20 monoclonal antibodies such as rituximab are still considered third-line agents in the European Academy of Dermatology and Venereal Diseases guidelines published in 2015 [26]. Recently, anti-CD20 antibodies have been recommended as the first choice only for moderate to severe and/or resistant pemphigus. Following administration of rituximab, a rapid and sustained decrease in circulating and tissue B lymphocytes is observed, lasting at least 6 to 12 months. Recent evidence suggests that it also affects T lymphocytes [20]. Rituximab treatment reduced the total corticosteroid dose required for clinical remission, thus reducing side effects secondary to long-term high-dose corticosteroids. A recent retrospective case-control study involving 40 patients showed that patients previously treated with rituximab treated with conventional therapy were able to reduce their monthly prednisone dose by 73% from a median of 658.6 mg/month to 177.2 mg/month [12].

It should be administered IV as a slow infusion (four to 6 hours). There are no standardized protocols for the use of rituximab in autoimmune bullous diseases. There is much debate about the optimal dose of Rituximab in pemphigus. Two main protocols are used: the rheumatoid arthritis protocol, which consists of two 1,000 mg infusions two weeks apart, and the lymphoma protocol, which consists of four 500 mg once-weekly infusions [36]. No differences in percent remission and disease-free time were observed in either protocol. They can be used alone or in combination with intravenous immunoglobulin, plasmapheresis and immunoadsorption. It can also be applied to patients already taking prednisone and immunosuppressive drugs; dose reduction and suspension of the latter should be accelerated, due to the increased risk of infection [20].

Intravenous Immunoglobulin (IVIg); derived from a pool of donors, IVIg consists of human plasma-derived IgG, sugars, salts and solvents [36]. It is thought that IVIg functions by saturating the neonatal Fc receptor, thereby increasing the catabolism of the patient’s serum antibodies containing pathogenic autoantibodies [25]. IVIg is mostly used in patients resistant to corticosteroid and immunosuppressive treatments. 2 gr/kg is applied in each session. In studies, it has been shown that the application of 0.4 g/kg/day for 5 consecutive days is effective in the treatment [20, 36]. It can also be combined with rituximab. Slow 5–5.5 hour infusions can minimize infusion reactions [13]. A major benefit of IVIg is its few side effects. The most common side effects are headache, dyspnea, tachycardia, and abdominal discomfort. The most serious adverse events are aseptic meningitis and cerebrovascular accidents, occurring in <1% of PV patients treated with IVIg [13]. It can be used on pregnant women.

TNF-α inhibitors; TNF-α is one of the cytokines involved in acantholysis. Although the use of Infliximab and Etanercept as a case report appears to be effective in the treatment of PV, there are conflicting results [20].

Topical treatment; PV is largely managed with systemic therapy, but skin and mucosal care are extremely important. For this purpose, topical corticosteroids and, if there is a risk of infection, antibiotic creams are often added to the treatment. It has also been reported that tacrolimus and pimecrolimus, pilocarpine gel 4%, nicotinamide gel 4%, 0.1% sulfadiazine creams are also beneficial [37].

During the treatment period, patients should be followed closely for diabetes, hypertension, heart failure, myopathy, osteoporosis, avascular bone necrosis, glaucoma, cataract due to corticosteroids, infections, especially respiratory tract infections, hepatitis, CMV reactivation or hematological abnormalities (anemia, leukopenia) as a result of immunosuppression.

Future Therapies; CAAR-T Therapy, BTK inhibitor and p38MAPK inhibitor are included.

CAAR-T Therapy; T cells expressing chimeric autoantibody receptors (CAAR-T cells) that target antibody-producing B cells are one of the latest proposed avenues for treating for autoimmune conditions.

Bruton tyrosine kinase (BTK) Inhibitor; Bruton tyrosine kinase (BTK) is expressed in B cells and innate immune cells, acting as an essential signaling element in multiple immune cell pathways. Selective BTK inhibition has the potential to target multiple immune-mediated disease pathways. Rilzabrutinib is an oral, reversible, covalent BTK inhibitor designed for immune-mediated diseases [38]. One of the new potential treatments for pemphigus, the BTK inhibitor rilzabrutinib (PRN1088) was recently tested in patients with PV in a phase II trial and controlled 50–56% of lesion activity in patients in a mean of 4 weeks [39]. Thus, inhibition of kinases such as BTK shows promising potential for future treatment of PV.

p38MAPK inhibitor (SB202190); In a murine model of pemphigus, p38MAPK inhibition prevented blister formation. On the other hand, in a study, the formation of blisters in the mucosa could not be prevented by a p38MAPK inhibitor, and they claimed that, unlike the epidermis, the ultrastructural changes of blister formation and desmosomes were independent of p38MAPK in the oral mucosa [40].

11. Prophylaxis against side effects in prolonged corticosteroid

Basic screening and prophylaxis of osteoporosis, ophthalmological evaluation, vitamin D and calcium supplementation during corticosteroid therapy, treatment with bisphosphonates (ie alendronate, risedronate) in patients at risk of developing osteoporosis (postmenopausal women and > 50 years and > 3 months on corticosteroid treatment), clinical systemic antifungals, antiviral and antibiotic therapy if needed, use of H2-blockers or proton pump inhibitors, antithrombotic prophylaxis in case of high thrombosis risk, psychological support if necessary, physiotherapy if long-term corticosteroid therapy is required [41].

12. Prognosis

The mortality rate of PV is estimated about 5–10%. Death is mainly a result of corticosteroid and immunosuppressant side effects. In particular, patients with persistent PV may develop serious infections secondary to high-dose corticosteroid use. Most patients with relapsing forms of the disease require a long course of treatment of 10 years or more [42].

13. Pemfigus vulgaris in children

PV is the most common type in the pediatric group among all pemphigus types, excluding endemic pemphigus foliaceus [43]. The pediatric variant is divided into two, childhood PV (0–12 years) and adolescent (juvenile) PV (13–18 years) [44]. Most patients have mucocutaneous involvement, both in childhood and in the juvenile form. Oral, nasal, ocular and anal mucous membranes are involved. The frequency of genital involvement is high in both groups [45]. The clinical picture is similar to that in adults. Loose bullae on intact or erythematous skin open easily and become eroded and crusted lesions. Antibody titrations can be detected in the serum in most of patients [43]. Nikolsky’s sign is positive.

Systemic steroid as in adults, is the cornerstone of treatment [45]. Systemic side effects develop in two-thirds of patients treated with systemic steroids. The most common side effects are; Cushing’s syndrome (65%), growth retardation (50%) and infection (50%). Prednisone dose is started at 40–60 mg/day, when new lesion growth stops, it is gradually reduced and adjuvant therapy is added. Many adjuvant agents such as AZA, dapsone, mycophenolate mofetil, cyclophosphamide, methotrexate, cyclosporine, plasmapheresis, IVIg and rituximab have been used in the treatment of children as in adults. Data on the use of rituximab therapy in pediatric patients are limited. The youngest case treated with rituximab was a 4-year-old girl [44]. There are partial and complete remission reports in the literature. There is no standard dosing regimen in children. The lymphoma protocol was used in most of the published cases. Treatments usually last 2–3 years and the prognosis is better than in adult patients [46].

14. Pemfigus vulgaris during pregnancy

PV is extremely rare in pregnancy. On the other hand, pregnancy may accelerate or increase PV, as reported in well-known autoimmune diseases such as systemic lupus erythematosus [47]. Babies of mothers with pemphigus may be affected by the disease in many different ways, from stillbirth to transient PV lesions in newborns, due to transplacental transmission of pathogenic anti-Dsg antibodies [48]. The more uncontrolled the disease in the mother and the higher the titers of Dsg antibodies in the mother’s serum or umbilical cord blood, the worse the possible outcomes [48]. PV seen during pregnancy can affect the mother, delivery and fetus. While the disease exacerbates mostly in the first, second trimester and postpartum periods, it calms down in the third trimester [49]. The reason for this is probably the increase in the endogenous chorionic corticosteroid hormone and the resulting immunosuppression [50, 51]. However, no change is observed in some patients during pregnancy, and these patients may remain in remission [49]. The postpartum disease worsens in all pemphigus patients who are not treated during pregnancy [52]. If the disease worsens in the first trimester, medical termination of pregnancy may be considered. If the worsening of the disease occurs in the second or third trimester, steroids are a safe treatment option [53].

In the publications on the treatment of autoimmune bullous diseases in pregnancy, it is stated that topical/systemic steroids and AZA can be used safely. In a small number of case reports, it has been reported that rituximab, IVIg, and dapsone may also be safe [54]. AZA is the most commonly used non-steroidal immunosuppressant in pemphigus. If it is necessary to give, the lowest dose should be preferred to prevent fetal damage [55]. The pregnancy category is D. Cyclosporine is believed to be less effective in the treatment of pemphigus but is the most reliable agent in pregnancy [56]. MMF, cyclophosphamide, and methotrexate are drugs that are not preferred or even contraindicated during pregnancy [57].

15. Vaccination in pemphigus patients

Administration of live vaccines is contraindicated when using adjuvant immunosuppressants and rituximab. Vaccination against seasonal influenza, H1N1, tetanus and pneumococci are recommended in patients receiving oral corticosteroids or immunosuppressives. During systemic immunosuppression, the level of protection after vaccination raises question marks [26]. On the other hand, it has been reported in the literature that pemphigus vulgaris is seen after tetanus diphtheria, hepatitis B and influenza vaccine applications, and that the disease exacerbates after influenza vaccine use [58]. We do not have any data on which patients vaccination will cause disease reactivation [59].

Although COVID mRNA vaccines may cause autoimmune bullous disease activation, it is recommended not to abandon the vaccination and to treat the existing picture in case of disease activation [60].

Based on vaccination experience, when vaccines for COVID-19 are available, dermatologists may advise vaccination 12–20 weeks after completion of a treatment cycle with rituximab or extend dosing intervals so that a minimum time of 4 weeks precedes the next drug infusion [61].

Limited data suggest that patients with autoimmune bullous disease receiving immunomodulatory therapies are not primarily at risk for serious or fatal COVID-19 [60].