Comprehensive understanding of idiopathic guttate hypomelanosis: clinical and histopathological correlation.

Abstract

BACKGROUND: The histological findings associated with idiopathic guttate hypomelanosis (IGH) are hyperkeratosis, an atrophic epidermis, and flattened rete ridges. In addition, a decreased melanin content and reduced numbers of melanocytes are reported features. However, there are few recent studies that have been published on the histopathology of IGH and no comparative studies are available on the skin lesions and perilesional skin of patients with IGH.

OBJECTIVES: The goals of this study were to identify the clinical and histopathological features of IGH and determine their correlation. We evaluated the clinical features and the histopathological differences between the skin lesions and the perilesional skin in patients with IGH.

METHODS: A clinical survey was carried out on 47 patients with IGH. Specimens from skin lesions and perilesional skin were stained with hematoxylin-eosin, Fontana-Masson, MART-1, and NKI/beteb. We also studied the ultrastructure of four cases.

RESULTS: About 30% of the patients had their initial lesions prior to 20 years of age. The arm was the most commonly affected site (53%). Histologically, we found hyperkeratosis in 18 cases (38.3%), but epidermal atrophy was present in only five cases (10.6%), and flattened rete ridges in seven cases (14.9%) compared to the normal skin. Epidermal atrophy was more frequently found at nonsun-exposed areas. The IGH lesions demonstrated decreased melanin pigment and reduced numbers of melanocytes by NKI/beteb and MART-1. The ultrastructural evaluation showed degenerative melanocytes and decreased melanosomes. One specimen had normal melanocytes with decreased melanosomes.

CONCLUSIONS: Idiopathic guttate hypomelanosis is a disorder with multifactorial etiology; its pathogenesis may depend on various factors such as patient age and sun-exposure. Histopathologically, hyperkeratosis was frequently found; however, the other characteristic findings such as epidermal atrophy and flattened rete ridges were relatively rare.