Dermoscopy of Hypo-pigmented Lesions in Children

Among the most common disorders of hypo-pigmentation in children are pityriasis alba, vitiligo, nevus depigmentosus, postinflammatory hypopigmentation and tinea versicolor ; while idiopathic guttate hypomelanosis and hypopigmented mycosis fungoides comes late.

Pityriasis alba : is a low-grade type of eczema/dermatitis mostly occurring in children and young adults , usually seen as dry, fine-scaled, pale patches on the face .

Vitiligo : is an acquired, autoimmune, idiopathic disorder characterized by circumscribed depigmented macules and patches with or without leukotrichia .

Nevus depigmentosus : is a localized hypopigmentation which most of the time is congenital. It is considered as a form of cutaneous mosaicism.

Postinflammatory hypopigmentation : is an acquired partial or total loss of skin pigmentation occurring after cutaneous inflammation. Many cutaneous inflammatory conditions lead to postinflammatory hypopigmentation in children as :Atopic dermatitis , Insect bite reactions, Psoriasis, Stevens-Johnson syndrome ….; Infections as Chickenpox, Impetigo …..; Cutaneous injuries from burns, irritants .All tend to induce postinflammatory hypopigmentation rather than hyperpigmentation .

Pityriasis versicolor or tinea versicolor : is a fungal infection of the superficial layer of skin caused by Malassezia yeasts. It is clinically characterized by hyperpigmented or hypopigmented, round to oval lesions covered with scales commonly found on the trunk, upper arms and face. Although it's common in adults but it can be seen in older group of children .

Idiopathic guttate hypomelanosis : is an acquired leukoderma found in all races; Its pathogenesis is unknown but may depend on various factors such as patient age and sun-exposure. Clinically, the lesions are porcelain-white macules, usually 2-6 mm in size, but sometimes they are larger. The borders are sharply defined, often angular and irregular with normal skin markings.

Mycosis fungoides, the most common primary cutaneous T-cell lymphoma: is a neoplastic disease characterized by classical non-infiltrated lesions (patches), plaques, tumors, and erythrodermic stages .It is considered a serious condition that has been seen before in children. Hypopigmented mycosis fungoides is one of its variants that is presented by hypopigmented-to-achromic lesions, sometimes with a vitiligo-like aspect.

In addition to clinical picture, Woods light examination and potassium hydroxide scrapping for scaly hypopigmented macules and histopathological evaluation are used to be the gold standard tests for diagnosis of those hypopigmented lesions in children.

Dermoscopy is a noninvasive diagnostic tool that permits the visualization of morphological features that are not visible to the naked eye thus representing a link between macroscopic clinical dermatology and microscopic dermatopathology . Recently, awareness and knowledge of dermoscopy have increased tremendously in many countries in diagnosis of many skin conditions .

Dermoscopy may be a helpful as a non-invasive tool in assisting the differential diagnosis of several hypopigmented macular lesions and has the potential to improve the diagnostic accuracy. New studies have documented dermoscopic features in vitiligo , While very few reports have documented the dermoscopic features of the other hypopigmented lesions.