Dermoscopic features of plaque psoriasis and its differentials.
Psoriasis is a chronic inflammatory skin disease, which is mainly characterized with erythematous indurated plaques with squams such as many other inflammatory skin diseases. Also different clinical subtypes of psoriasis can show distinctive clinical appearances. As an example, inverse psoriasis does not have squams and resemble erythema intertrigo; or erythrodermic variant cannot be distinguished from other erythroderma causes sometimes. From reasons above, differential diagnosis of psoriasis should be done carefully to manage a chronic and long-term treatment required disease appropriately. Histopathologial examination is gold standard technique for certain diagnosis; however, dermoscope is a noninvasive and easily applicable diagnostic tool with high specificity. In this chapter, we discuss dermoscopic differential diagnosis of psoriasis.
Psoriasis is a chronic inflammatory skin disease that progresses with remission and exacerbations [1, 2]. It constitutes an important percentage, approximately 6–8% of patients who apply to dermatology clinics . Due to its high prevalence and chronic course, it is important to diagnose it early and clearly to manage patient appropriately and avoid functional losses as much as possible. In addition, in some situations that should be intervened swiftly such as erythrodermic psoriasis or generalized pustular psoriasis; the sooner we diagnose, the better we take control of disease setting.
In diagnosis of psoriasis, usually clinical observation is enough; however, in doubtful cases, histopathological examination is required as gold standard technique. However, it requires an invasive procedure and needs time for pathological preparation. With dermoscopy, we can mostly distinguish psoriasis from other resembling diseases in clinic noninvasively. Despite it not being gold standard, easily applicable and noninvasive properties of dermoscopy make it a helpful diagnostic tool and reduce the need of performing biopsies.
2. Dermoscopy of psoriasis types and differentials
2.1 Plaque psoriasis
Plaque psoriasis is the most common clinical subtype of psoriasis with 90% of all cases . It is characterized by erythematous, well-defined, and usually indurated plaques greater than 1 cm in size with white-silvery scales on them (Figure 1). They can vary in size and may coalesce. Especially rapidly progressing lesions can be seen in annular configuration (Figure 2) [4, 5]. Removal of psoriatic scales may cause pinpoint bleedings, which is called Auspitz sign. Psoriatic plaques are mostly located in the scalp, trunk, lumbosacral area, and extensor surfaces of extremities (Figure 3) .
2.1.1 Dermoscopy of plaque psoriasis
Dermoscopic examination of a psoriasis plaque should be done in three categories: background, vessels, and scales. Examination should be done with minimal pressure to visualize vessels better and with immersion oil if possible.
In dermoscopic examination of plaque psoriasis with handheld dermoscope, we usually see regularly distributed dotted vessels in a reddish-pinkish background and white scales (Figure 4) . In some cases, background can be grayish-white due to highly hyperkeratotic scales (Figure 5).
Apart from regular distribution, vessels can be distributed scattered, in clusters, in rings, and patchy (Figure 6a). In higher magnifications (with videodermoscopy), these dotted vessels can be seen as bushy capillaries, globules, radial capillaries, globular rings, hairpin capillaries, and comma vessels in descending order  (Figure 6b). Rarely dot blood hemorrhages can be seen in vessel locations (Figure 5). Scales can be distributed diffuse, patchy, central, or peripheral in descending order; however, white color is key point for scales [8, 9].
2.1.2 Dermoscopic differential diagnosis of plaque psoriasis
Differential diagnosis of plaque psoriasis should be done with skin diseases, which are characterized by erythematous plaques with scales such as dermatitis, tinea corporis, pityriasis rosea, pityriasis rubra pilaris, lichen planus, and non-pigmented squamous cell carcinoma in situ.
In dermoscopic examination of dermatitis, we usually see patchy or scattered distributed dotted vessels with yellow globules (corresponding to sero-crusts) . Background can be erythematous or not depending on lesions phase (acute or chronic). Hemorrhagic crusts can be seen as well secondary to traumatization (Figure 7).
In dermoscopic examination of tinea corporis, we usually see peripherally located dotted vessels and rough white scales (Figure 8). In contrast with psoriasis, dotted vessels are not regularly distributed and not uniform. In addition, scales are only located peripherally, tend to peel outward, and shaped in moth-eaten pattern .
Pityriasis rubra pilaris shows dotted and more frequently linear vessels, perifollicular yellow-orange halos, follicular plugs with central hair on them (Figure 9). Scales can be yellowish or whitish. Background is usually dark or yellowish red [7, 12].
Squamous cell carcinoma in situ and psoriasis can be challenging especially in solitary plaques. Dermoscopic clues for non-pigmented squamous cell carcinoma in situ are dotted or glomerular vessels in clusters in the center and arranged in lines at the periphery with yellowish white scales (Figure 10) [13, 14].
Dermoscopic features of plaque psoriasis and its differentials are summarized in Table 1.
|Background||Vessel types||Vessel arrangement||Scales||Additional features|
Whitish (due to hyperkeratotic scales)
|Skin colored-pinkish||Dotted||Scattered/patchy||Yellowish||Irregularly distributed dot blood hemorrhages due to traumatization|
|Reddish||Dotted||Peripheral||White and rough; peripheral; moth-eaten pattern; tend to peel outwards|
|Dark red/yellowish red||Linear and/or dotted||Scattered||Yellowish-whitish; follicular||Perifollicular yellow-orange halos, follicular plugs, central hair|
|Pinkish||Glomerular or dotted||Regularly in center, may organize in lines at the periphery||Yellowish white scales||Peripheral actinic keratosis areas may help (white and wide follicular openings, rosettes)|
2.2 Guttate psoriasis
Guttate psoriasis, a psoriasis variant that is more common in pediatric population and young adults. Distinctly from other variants, we know that guttate psoriasis is selectively triggered by beta hemolytic streptococcal infections . It is characterized by erythematous, well-defined flat papules/plaques lower than 1 cm in size with white-silvery scales on them. Lesions mostly located in the trunk and extremities (Figure 11a and b).
2.2.1 Dermoscopy of guttate psoriasis
Dermoscopic features of guttate psoriasis are very similar with plaque psoriasis, which is characterized by regularly distributed dotted vessels in a reddish background and white scales on them (Figure 12). Due to guttate psoriasis’ smaller lesion sizes (lower than 1 cm in diameter), findings may be insignificant when compared with plaque psoriasis (Figure 13).
2.2.2 Dermoscopic differential diagnosis of guttate psoriasis
Differential diagnosis of guttate psoriasis should be done with skin diseases, which are characterized by erythematous papules/small plaques with scales. Pityriasis rosea, lichen planus, nummular dermatitis, secondary syphilis, tinea corporis, pityriasis lichenoides chronica, and disseminated eruptive porokeratosis may count as differential. (Dermatitis and tinea corporis will not be mentioned because they were discussed above.)
Dermoscopic examination of pityriasis rosea shows irregular distributed dotted vessels and peripheral thin white scale (Figure 14) . Scales tend to peel outward as in tinea corporis. But note the white scale is not rough and vessels are not in the same distribution with scales. Background is generally skin-colored or slightly pinkish.
In dermoscopic examination of lichen planus, key point is detecting Wichkam striaes, which cannot be seen macroscopically sometimes. In fair-skinned patients, dotted and linear vessels around Wickham striae make these structures more visible (Figure 15); however, in dark-skinned patients, absence of peripheral vascular structures around Wichkam striaes may lead to misdiagnosis .
In dermoscopic examination of secondary syphilis, yellowish-orange background and absence of vascular structures are key points (Figure 16) . Scales may be present, however, thinner and smaller when compared with psoriatic scales.
Dermoscopic features of guttate psoriasis and its differentials are summarized in Table 2.
|Background||Vessel types||Vessel arrangement||Scales||Additional features|
|Reddish-pinkish||Dotted||Regular||Whitish-grayish, thin and small|
|Pinkish||Dotted (vascularization is not dominant)||Patchy||White, thin, peripheral and tend to peel outwards “collarette sign”|
|Pinkish, violaceus||Dotted or absent||Aroud Wickham striae||Whitish, patchy distributed, thin and small|
|Yellowish-orange||Absent||White and thin|
|Pinkish, yellowish-orange||Dotted or linear||Focal||White, patchy, thin|
|Yellowish-brown||Unsignificant||White, small||Peripheral railway like double lines called “cornoid lamella”|
2.3 Inverse psoriasis
Inverse psoriasis is another clinical variant of psoriasis, which involves flexural areas such as axillary, inguinal, and inframammary . The prevalence of inverse psoriasis is not clear and varies in 3–36% because of diagnostic challenges . And also it is controversial that if genital involvement is a part of inverse psoriasis; however, we include genital involvement under this topic for convenience of expression.
Inverse psoriasis is typically present with well-defined erythematous plaques located in flexural areas (Figure 19a and b). It can present with or without typical psoriasis plaques. In contrast with plaque and guttate psoriasis, scales are insignificant or absent.
Genital involvement shares similar clinical features with inverse psoriasis such as well-defined erythematous papules and plaques (Figure 20). However, occlusion in the genital areas is not as much as flexural areas, scales could be more visible in the genitals.
2.3.1 Dermoscopy of inverse psoriasis
Dermoscopic features of inverse psoriasis are characterized by regularly distributed dotted vessels on reddish background (Figure 21). In contrast with other variants, scales are absent. Absence of scales enhances visualization of vascular structures. Consequently, dermoscopic differential diagnosis of flexural dermatosis mainly leans on evaluation of vascular structures.
2.3.2 Dermoscopic differential diagnosis of inverse psoriasis
Differential diagnosis of inverse psoriasis should be done with skin diseases, which present with erythematous patches/plaques in flexural and genital areas. Mechanical intertrigo, seborrheic dermatitis, lichen planus inversus, and fungal/bacterial infections may count as differential. Because no clear dermoscopic features have been defined for mechanical intertrigo and flexural infections, we will discuss dermoscopic features of seborrheic dermatitis and lichen planus inversus under this topic.
The main dermoscopic features of seborrheic dermatitis of flexural areas are irregularly distributed linear, blurry vessels . As we mentioned before, we do not see classical yellowish scales of seborrheic dermatitis in flexuras.
When we review the literature so far, there are only three reports about dermoscopic features of lichen planus inversus. In all of these reports, dermoscopic features of only pigmented variant of lichen planus inversus were evaluated and defined as diffuse brown patches containing multiple granular gray-brown dots [23, 24, 25]. In our clinical practice, we see non-pigmented lichen planus inversus more than pigmented subtype. According to our dermoscopic experience, Wickham striae, which is seen in lichen planus inversus, tends to be in “starry sky” or “radial streaming” pattern rather than reticular pattern. Background is usually pinkish or violaceous. Dotted vessels usually encircle Wickham striae (Figure 22).
Dermoscopic features of inverse psoriasis and its differentials are summarized in Table 3.
|Background||Vessel types||Vessel arrangement||Additional features|
|Pinkish||Linear, blurry vessels||Irregular|
|Pinkish, violaceus||Dotted or absent||Aroud Wickham striae||According to our dermoscopic experience, Wickham striae, which is seen in lichen planus inversus, tends to be in “starry sky” or “radial streaming” pattern|
2.4 Pustular psoriasis
Pustular psoriasis is a rare clinical variant of psoriasis, which is characterized by sterile pustules on an erythematous skin (Figure 23). It could be either local or generalized . In generalized pustular psoriasis, concomitant fever, malaise, dehydration may also be present .
2.4.1 Dermoscopy of pustular psoriasis
Dermoscopic features of pustular psoriasis are characterized by regularly distributed dotted vessels with milky globules (corresponding to sterile pustules) on reddish background (Figure 24) . Attention should be paid on non-follicular localization of pustules. Typical vascular structures are seen. Nonspecific yellow crust may be seen. Dermoscopic features are same in both localized and generalized subtypes.
2.4.2 Dermoscopic differential diagnosis of pustular psoriasis
Dermoscopic differential diagnosis of pustular psoriasis should be done with acute generalized exanthematous pustulosis (AGEP). In life-threatening clinical conditions such as generalized pustular eruptions, rapid and right diagnosis is essential, and dermoscope is very helpful at that point. In both pustular psoriasis and AGEP, pustules are sterile, disseminated, may coalesce, and be non-follicular. Thereby, we cannot distinguish these two situations by their clinical view only. In dermoscopic examination of both pustular psoriasis and AGEP, non-follicular milky globules on reddish background are seen . Discriminately, in pustular psoriasis we see regularly distributed dotted vessels (Figure 24). In dermoscopic examination of AGEP, background is usually pinkish and vascular structures are absent (Figure 25) .
2.5 Erythrodermic psoriasis
Erythroderma is a life-threatening condition, which is defined as desquamation and erythema of more than 90% of body surface area . Erythrodermic variant of psoriasis (Figure 26) generally occurs due to poor control of disease, withdrawal of anti-psoriatic treatments, triggering drug intake, underlying systemic infections or conditions . Clinical clues for erythrodermic psoriasis diagnosis are known history of psoriasis, psoriatic nail changes, presence of psoriatic arthritis. However, if none of the mentioned features is present, dermoscopy could be a game-changer.
2.5.1 Dermoscopy of erythrodermic psoriasis
Dermoscopic features of erythrodermic psoriasis are the same as other psoriasis variants. Regularly distributed dotted vessels on a reddish background, and patchy white scales are seen (Figure 27) .
2.5.2 Dermoscopic differential diagnosis of erythrodermic psoriasis
Dermoscopic differential diagnosis of erythrodermic psoriasis includes dermatosis that can present with erythroderma such as atopic dermatitis, mycosis fungoides, and pityriasis rubra pilaris (Pityriasis rubra pilaris will not be mentioned because it was discussed above.)
Dermoscopic examination of atopic dermatitis shows typical dermatitis features. Yellowish globules (corresponding to sero-crusts) and patchy distributed dotted vessels on a pinkish background are demonstrative (Figure 28) .
Dermoscopic features of erythrodermic mycosis fungoides are a combination of linear and dotted vessels on a pale pinkish background (Figure 29) . Some short linear vessels may be curved and named as “spermatozoon-like” vessels.
Dermoscopic features of erythrodermic psoriasis and its differentials are summarized in Table 4.
|Background||Vessel types||Vessel arrangement||Scales||Additional features|
|Reddish||Dotted||Regular||White, scattered-patchy scales|
|Pinkish (pale)||Linear and dotted||Scattered||Whitish scales can present.||.|
Psoriasis is a common skin disease with different clinical presentations. Generally, clinical evaluation is enough for diagnosis, though dermoscope is a helpful and noninvasive examination technique that enhances true diagnosis ratio. Knowing psoriasis’ and its differentials’ dermoscopic features may reduce requirement for histopathological examination and also makes rapid diagnosis possible in life-threatening conditions such as erythroderma. Note that regularly distributed dotted vessels on a reddish background are the most important clues for any variant of psoriasis. In doubtful cases, histopathological examination should be done for verifying the diagnosis as a gold standard technique.
All photos used in this chapter were taken by Dr. Ece Gokyayla with iPhone (XS) and dermatoscope (DermLite, DL4 model, 3Gen, USA) connected to an iPhone (XS) via adapter (DermLite Connection Kit MagnetiConnect). Immersion oil was not used.
Conflict of interest
The authors declare no conflict of interest and no funding source.
Gül Ü. Psoriasis. Sağlığın Başkenti Dergisi. 2010; 16:18-21
Griffiths CEM, Camp RDR, Barker JNWN. Psoriasis. In: Burns T, Breathnach S, Cox N, Griffiths C, editors. Rook’s Textbook of Dermatology. 7th ed. Oxford: Blackwell; 2004. pp. 35.1-35.69
Braun-Falco O, Plewig G, Wolff HH, Burgdorf WHC. Dermatology. 2nd ed. Berlin: Springer-Verlag Berlin Heidelberg; 2000. pp. 585-610
Griffiths CE, Barker JN. Pathogenesis and clinical features of psoriasis. Lancet. 2007; 370(9583):263-271. DOI: 10.1016/S0140-6736(07)61128-3
Langley RG, Krueger GG, Griffiths CE. Psoriasis: Epidemiology, clinical features, and quality of life. Annals of the Rheumatic Diseases. 2005; 64(Suppl 2):ii18-ii23; discussion ii24-5. DOI: 10.1136/ard.2004.033217
Weigle N, McBane S. Psoriasis. American Family Physician. 2013; 87(9):626-633
Jha AK, Lallas A, Sonthalia S, Jhakar D, Udayan UK, Chaudhary RKP. Differentiation of pityriasis rubra pilaris from plaque psoriasis by dermoscopy. Dermatology Practical & Conceptual. 2018; 8(4):299-302. DOI: 10.5826/dpc.0804a10
Golińska J, Sar-Pomian M, Rudnicka L. Dermoscopic features of psoriasis of the skin, scalp and nails - A systematic review. Journal of the European Academy of Dermatology and Venereology. 2019; 33(4):648-660. DOI: 10.1111/jdv.15344
Golińska J, Sar-Pomian M, Rudnicka L. Dermoscopy of plaque psoriasis differs with plaque location, its duration, and patient's sex. Skin Research and Technology. 2021; 27(2):217-226. DOI: 10.1111/srt.12933
Errichetti E, Stinco G. Dermoscopy in general dermatology: A practical overview. Dermatology and Therapy. 2016; 6(4):471-507. DOI: 10.1007/s13555-016-0141-6
Lekkas D, Ioannides D, Lazaridou E, Lallas A, Apalla Z, Vakirlis E, et al. Dermatoscopy of tinea corporis. Journal of the European Academy of Dermatology and Venereology. 2020; 34(6):e278-e280. DOI: 10.1111/jdv.16277
Abdel-Azim NE, Ismail SA, Fathy E. Differentiation of pityriasis rubra pilaris from plaque psoriasis by dermoscopy. Archives of Dermatological Research. 2017; 309:311-314
Wozniak-Rito AM, Rudnicka L. Bowen's disease in Dermoscopy. Acta Dermatovenerologica Croatica. 2018; 26(2):157-161
Zalaudek I, Argenziano G. Dermoscopy of actinic keratosis, intraepidermal carcinoma and squamous cell carcinoma. Current Problems in Dermatology. 2015; 46:70-76. DOI: 10.1159/000366539
Saleh D, Tanner LS. Guttate Psoriasis. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2021
García-García B, Munguía-Calzada P, Aubán-Pariente J, Argenziano G, Vázquez-López F. Dermoscopy of lichen planus: Vascular and Wickham striae variations in the skin of colour. The Australasian Journal of Dermatology. 2019; 60(4):301-304. DOI: 10.1111/ajd.13052
Mathur M, Acharya P, Karki A, Shah J, Kc N. Dermoscopic clues in the skin lesions of secondary syphilis. Clinical Case Reports. 2019; 7(3):431-434. DOI: 10.1002/ccr3.1999
Errichetti E, Lacarrubba F, Micali G, Piccirillo A, Stinco G. Differentiation of pityriasis lichenoides chronica from guttate psoriasis by dermoscopy. Clinical and Experimental Dermatology. 2015; 40(7):804-806. DOI: 10.1111/ced.12580
Idoudi S, Dalle S. Dermoscopie de la porokératose actinique disséminée superficielle [Dermoscopy of disseminated superficial actinic porokeratosis]. Annales de Dermatologie et de Vénéréologie. 2020; 147(12):914-915. French. DOI: 10.1016/j.annder.2020.05.003
Micali G, Verzì AE, Giuffrida G, Panebianco E, Musumeci ML, Lacarrubba F. Inverse psoriasis: From diagnosis to current treatment options. Clinical, Cosmetic and Investigational Dermatology. 2019; 12:953-959. DOI: 10.2147/CCID.S189000
Omland SH, Gniadecki R. Psoriasis inversa: A separate identity or a variant of psoriasis vulgaris? Clinics in Dermatology. 2015; 33(4):456-461. DOI: 10.1016/j.clindermatol.2015.04.007
Errichetti E, Lacarrubba F, Micali G, Stinco G. Dermoscopy of Zoon's plasma cell balanitis. Journal of the European Academy of Dermatology and Venereology. 2016; 30(12):e209-e210. DOI: 10.1111/jdv.13538
Robles-Méndez JC, Rizo-Frías P, Herz-Ruelas ME, Pandya AG, Ocampo CJ. Lichen planus pigmentosus and its variants: Review and update. International Journal of Dermatology. 2018; 57(5):505-514. DOI: 10.1111/ijd.13806
Imbernón-Moya A, Churruca-Grijelmo M, Martínez-Pérez M, Lobato-Berezo A. Dermoscopic features of lichen planus Pigmentosus-Inversus. Actas Dermo-Sifiliográficas. 2015; 106(10):857-859. English, Spanish. DOI: 10.1016/j.ad.2015.06.007
Murzaku EC, Bronsnick T, Rao BK. Axillary lichen planus pigmentosus-inversus: Dermoscopic clues of a rare entity. Diagnosis: Lichen planus pigmentosus (LPP). Journal of the American Academy of Dermatology. 2014; 71(4):e119-e120. DOI: 10.1016/j.jaad.2014.01.881
Hoegler KM, John AM, Handler MZ, Schwartz RA. Generalized pustular psoriasis: A review and update on treatment. Journal of the European Academy of Dermatology and Venereology. 2018; 32(10):1645-1651. DOI: 10.1111/jdv.14949
Bachelez H. Pustular psoriasis and related pustular skin diseases. The British Journal of Dermatology. 2018; 178(3):614-618. DOI: 10.1111/bjd.16232
Errichetti E, Stinco G. Dermatoscopy in life-threatening and severe acute rashes. Clinics in Dermatology. 2020; 38(1):113-121. DOI: 10.1016/j.clindermatol.2019.10.013
Jha AK, Sonthalia S, Lallas A. Non-follicular milky globules-dermoscopy saves the day. Dermatology Practical & Conceptual. 2017; 7(2):35-36. DOI: 10.5826/dpc.0702a07
Cuellar-Barboza A, Ocampo-Candiani J, Herz-Ruelas ME. A practical approach to the diagnosis and treatment of adult erythroderma. Actas Dermosifiliogr. 2018; 109(9):777-790. DOI: 10.1016/j.ad.2018.05.011
Raychaudhuri SK, Maverakis E, Raychaudhuri SP. Diagnosis and classification of psoriasis. Autoimmunity Reviews. 2014; 13(4–5):490-495. DOI: 10.1016/j.autrev.2014.01.008
Errichetti E, Piccirillo A, Stinco G. Dermoscopy as an auxiliary tool in the differentiation of the main types of erythroderma due to dermatological disorders. International Journal of Dermatology. 2016; 55(12):e616-e618. DOI: 10.1111/ijd.13322