A rare dermatologic condition: Insights from three cases of circumscribed acral hypokeratosis

Circumscribed acral hypokeratosis (CAH) is a rare dermatologic condition primarily affecting acral surfaces, presenting as sharply demarcated, asymptomatic lesions with characteristic histopathological features, notably abrupt hypokeratosis, and variable thinning of the granular cell layer. Typically observed in middle-aged to elderly women as solitary lesions, CAH may occasionally present as multiple lesions, complicating diagnosis and management. We report four illustrative cases emphasizing the clinical and histologic variability of CAH. Case presentations have included lesions with clinical resemblance to psoriasis, fungal infection, and unspecified dermatitis, underscoring the diagnostic challenges associated with CAH. Histologically, all cases demonstrated abrupt transitions to hypokeratotic regions with minimal inflammatory response. Therapeutic responses were varied to topical calcipotriene, tazarotene, antifungal agents, and fractional laser therapy, highlighting the absence of standardized treatment guidelines. The pathogenesis remains uncertain, with proposed mechanisms ranging from acquired epidermal malformation, trauma, human papillomavirus infection, and genetic predisposition to disorders of keratinization and corneocyte adhesion. Notably, fractional laser therapy significantly lessened one refractory case, suggesting a potential novel treatment modality. Because of its benign yet chronic and refractory nature, accurate histopathologic diagnosis is crucial to facilitate appropriate management and surveillance for such rare potential complications as squamous dysplasia. This series underscores the importance of recognizing CAH's distinct clinicopathologic entity to guide effective clinical management.