The most common disorders of hypopigmentation in children are PA, vitiligo, nevus depigmentosus, and tinea versicolor. The localized form of nevus depigmentosus must be distinguished from an ash leaf spot, the earliest cutaneous manifestation of tuberous sclerosis, whereas the systematized form may be confused with hypomelanosis of Ito, another neurocutaneous disorder Nummular eczema Nummular eczema is intensely pruritic. This condition seems to be a variant of classic PA, showing a strong association with dermatophyte infection, especially tinea capitis. It may be related to lichenoid melanodermatitis. Characteristic morphology of pigmenting PA includes a central zone of bluish hyperpigmentation surrounded by a hypopigmented, slightly scaly halo of variable width.
Patients display lesions primarily on the face.
The lesions of tinea versicolor favor the upper trunk of adolescents. Potassium hydroxide examination of the associated scale reveals hyphal and yeast forms of Malessia furfur. Vitiligo Vitiligo is an acquired, progressive disorder, in contrast to nevus depigmentosus, which is a stable, congenital leukoderma. The face is a common site for vitiligo, but the distribution is most commonly around the eyes or mouth, and, in contrast to PA, the pigment loss is complete. The correct diagnosis is usually suggested by the age of the patient, fine scaling, hypopigmentation, and the distribution of lesions.