Circumscribed acral hypokeratosis: successful treatment of a potentially premalignant condition.

C ircumscribed acral hypokeratosis (CAH) is a rare benign dermatosis of unknown origin first described in 2002. This uncommon dermatosis is seen predominantly on the palms of adult women with a mean age of 65 years. Lesions have a predilection for the thenar or hypothenar eminence of the predominant palm and less frequently on the soles. Typically, the lesions are solitary, but multiple lesions have been reported. Circumscribed acral hypokeratosis has characteristic clinicopathologic features and runs a chronic course. Histologically, the lesions show a classic abrupt decrease in the thickness of the stratum corneum, forming a sharp stair between normal and involved acral skin. The lack of epidermal atypia or cornoid lamellae clearly differentiates CAH from its clinical mimics, Bowen disease and porokeratosis. Circumscribed acral hypokeratosis is generally considered a benign condition, but Kanitakis et al recently reported a case of CAH that underwent premalignant transformation and hypothesized that the absence of the horny layer rendered the underlying keratinocytes susceptible to photocarcinogenesis. This report emphasized the need for close follow-up and suggested that treatment of CAH lesions may be useful to prevent malignant transformation. We describe herein a patient who experienced a sustained complete clinical response after treatment with liquid nitrogen cryotherapy.