Dermoscopy in General Dermatology for Skin of Color

Enzo Errichetti, Aimilios Lallas, Enzo Errichetti, Aimilios Lallas

• Publisher: CRC Press
• Year: 2021
• eBook ISBN: 9781000434385
• Edition: 1
• Topic: Medicine
• Subtopic: Family Medicine & General Practice

Dermoscopy can be a useful tool to evaluate skin of color for general dermatologic diseases; however, it does require practitioners to be aware of many points of difference from patients with lighter phototypes. This highly illustrated text brings together the pioneering experience of international experts to document patients of phototypes IV to VI (from subcontinental Asian, North African, South American, to African skin).

Part I
Inflammatory and Infiltrative Diseases

1
Papulosquamous disorders

Enzo Errichetti, Balachandra Ankad, Shekhar Neema, Ahmed Sadek, Dalia Hossam, Abhijeet Kumar Jha, Feroze Kaliyadan, Jayasree Puravoor, Soumil Khare and Aimilios Lallas

DOI: 10.1201/9780367816483-1

1.1 Psoriasis

1.1.1 Introduction

Psoriasis is a chronic immune-mediated, inflammatory disease mainly involving the skin, nails and joints pathogenetically related to both genetic and environmental factors.^1,2 Cutaneous psoriasis is typically considered as a hyperproliferative disorder with an increased proliferation of keratinocytes resulting from a cascade of immunologic reactions driven by several cytokines.^1,2 The prevalence rate among dark-skinned populations varies according to the countries, yet it is generally lower than that of Caucasians.^1,2 Although psoriasis can manifest at any age, it generally presents two peaks of onset (20–30 and 50–60 years of age).^1,2

1.1.2 Clinical presentation

Several clinical variants of skin psoriasis do exist, with the most common one being plaque-type psoriasis (also known as psoriasis vulgaris).^1,2 This form typically presents with relatively symmetric, well-defined, brownish, violaceous or greyish plaques covered with silvery scales more commonly affecting the scalp, elbows, knees, trunk, genitalia and presacral and palmo-plantar areas (Figures 1.1A–1.6A).^1,2 Pruritus may be present, especially in lesions of the scalp.^1,2 Residual dyspigmentations (hyper- or hypopigmentations) after the lesions heal are quite common in skin of colour (Figures 1.7A and 1.8A).^1,2

Other common forms of psoriasis include guttate psoriasis (acute onset of multiple small scaly papules often triggered by a streptococcal pharyngitis), erythrodermic psoriasis (generalized erythema and scaling affecting >90% of the body surface), genital psoriasis (Figure 1.9A), palmo-plantar or diffuse pustular psoriasis (groups of pinpoint sterile pustules with or without plaques) and inverse psoriasis (well-demarcated plaques with no visible scaling involving the skin folds).^1,2 Follicular psoriasis (Figure 1.10A), psoriasis ostracea, psoriasis rupioides (Figure 1.11A), psoriasis figurata, psoriasis gyrata and annular psoriasis are examples of rare variants.^1,2

Finally, nail psoriasis is quite common (30%–50% of psoriatic patients) and may manifest with several ungual changes, such as nail pitting, crumbling, Beau lines and mottled lunula in case of matrix involvement and onycholysis, salmon patches, subungual hyperkeratosis and splinter haemorrhages in case of bed involvement.^1,2

1.1.3 Dermoscopy

The dermoscopic hallmarks of psoriasis are represented by diffuse white scales and uniform dotted vessels (Figure 1.1B), histologically corresponding to hyperkeratosis and tips of dilated vessels in regularly elongated dermal papillae (papillomatosis), respectively.^3–5 Notably, even though the prevalence of vascular structures in dark-skinned patients is lower than that in fair-skinned subjects, psoriasis is one the few papulosquamous dermatoses in which vessels are commonly seen on dermoscopy (60%–75% of cases).^6,7,8 This is because of the fact that the significant epidermal acanthosis typical of psoriasis makes the skin background lighter, thus enhancing the optical contrast with vessels (Figures 1.1B and 1.2B).⁶

In hyperkeratotic plaques, thick scales may cover the underlying vascular structures, yet removal of the scales may bring to light the typical vascular pattern.^3–6 However, analysis of the scaling pattern (colour and distribution) still remains the main dermoscopic clue in a significant proportion of dark-skinned patients, especially in areas having a thick skin (i.e., scalp or palmo-plantar areas) (Figures 1.3B–1.5B).⁶ Additionally, vessels are difficult to see also in initial/thin lesions as they are characterized by a limited papillomatosis on histology.^3–6 Pigmentary structures (especially focal or diffuse brown structureless areas resulting from basal layer hyperpigmentation) are also not uncommonly seen in psoriasis in ethnic skin (Figure 1.1B).^6,7

Further dermoscopic findings of psoriasis include focal structureless white areas (related to epidermal acanthosis) (Figure 1.1B) as well as haemorrhagic dots/areas, erosions and broken hairs resulting from scratching (Figure 1.6B), especially on the scalp and legs.^3–6 Additionally, dermoscopy can also help the clinician diagnose psoriasis retrospectively as the typical vascular pattern may also be observed in hypopigmented postinflammatory patches (Figures 1.7B and 1.8B).^3–5,8

The dermoscopic pattern of specific subtypes of psoriasis do not significantly differ from each other, except for the scaling amount.^3–5,8 Indeed, inverse psoriasis and psoriatic balanitis (Figure 1.9B) classically do not feature scales, whereas scalp and palmo-plantar psoriasis usually reveal a thick hyperkeratotic surface (Figure 1.4B).^3–5,8 Nevertheless, there are some clinical forms of psoriasis, which are not so uncommon in dark skin, that may show peculiar dermoscopic findings, such as follicular psoriasis, characterized by irregularly distributed follicular plugs associated with white scaling (Figure 1.10B) and rupioid psoriasis, which displays cone-shaped thick scales (Figure 1.11B).⁸

Figure 1.1 Plaque-type psoriasis in an Indian woman (A). Dermoscopy reveals diffuse white scales and un...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Dedication
• Contents
• List of contributors
• Preface
• Introduction
• Part I Inflammatory and infiltrative diseases
• Part II Infectious diseases
• Part III Hair, nail and mucosal diseases
• Index