Steroid-Induced Hypopigmentation of the Dorsal Hand: Clinicopathologic Correlation With Distinct Melan-A/SOX10 Findings.

Steroid-induced hypopigmentation (SIH) is an uncommon and often underappreciated complication of local corticosteroid therapy, especially in visible sites such as the dorsal hand. We report a case of a 51-year-old woman who developed an elongated hypopigmented patch following intralesional triamcinolone injection for hand pain. The lesion appeared several weeks after injection, was sharply defined, and tracked the extensor tendons without associated surface changes or significant atrophy. Histologic examination revealed a largely unremarkable epidermis with subtle atrophic changes and preserved melanocyte density as demonstrated by SOX10 staining. Notably, Melan-A staining was mostly absent or faint in occasional melanocytes, a feature we consider most characteristic of SIH and shared to some extent with idiopathic guttate hypomelanosis (IGH), but not seen in other hypopigmentary disorders such as vitiligo and postinflammatory hypopigmentation. Minimal dermal inflammation was observed, and no melanophages were present. This case emphasizes pathognomonic histologic and immunohistochemical features of SIH, in particular the characteristic Melan-A and SOX10 staining appearance in distinguishing SIH from its clinical mimickers. Underlying pathogenetic mechanisms and pertinent differential diagnoses are briefly reviewed. Considering the limited biopsy-based literature, this case adds additional histopathologic details that may improve diagnostic accuracy.