Clinical and dermoscopic patterns of idiopathic guttate hypomelanosis

Depigmented skin lesions are of great concern in society, especially in the Indian subcontinent. These comprise many infective and inflammatory conditions that cause apprehension and anxiety among patients due to the social stigma attached to these conditions. Idiopathic guttate hypomelanosis (IGH) appears similar to many depigmented lesions and differentiation of IGH from these conditions is difficult clinically as well as histopathologically. IGH is one of the common causes of acquired leukoderma. It is also called disseminated lenticular leukoderma. The etiology is yet not clearly delineated, probably multifactorial. Various etiological factors have been proposed including ultraviolet (UV) exposure, post-phototherapy (psoralen and UVA monotherapy, narrowband-UVB), aging, genetic factors, trauma, and autoimmunity. Clinically, it is characterized by multiple, discrete porcelain-white round to oval macules of 2–5 mm average size. It most commonly occurs in the elderly. The most common sites observed are chronically sun-exposed areas such as the arm, pretibial regions, and forearm extensors. It is not easy to differentiate IGH from other hypo and depigmented conditions such as vitiligo, pityriasis versicolor, extragenital lichen sclerosus et atrophicus, guttate morphea, and post-inflammatory hypopigmentation. It poses a diagnostic challenge to dermatologists. One has to differentiate depigmented lesions from vitiligo as it carries tremendous social implications as social stigma, especially in India. Research on dermoscopic evaluation is uncommon in the literature, despite the abundance of clinic-epidemiological and histological studies of IGH. Four dermoscopic patterns, namely, petaloid, amoeboid, feathery, and nebuloid have been described. These patterns are specific to IGH and help clinicians to differentiate many depigmented skin lesions from IGH in clinical practice. Patients often seek cosmetic treatment. There has been no standard therapy for this condition. Newer treatment modalities range from topical agents to procedure-based therapies and have enhanced the therapeutic armamentarium.