Focal acral hyperkeratosis: a rare cutaneous disorder within the spectrum of Costa acrokeratoelastoidosis.

Acrokeratoelastoidosis and focal acral hyperkeratosis share similar clinical features and identical histologic epidermal alterations. These disorders are distinguished solely on the basis of the absence of elastorrhexis in the latter. We present a case of focal acral hyperkeratosis in a 9-year-old girl. The lesions consisted of translucent polygonal papules clustered on the thenar regions of the palms and over the metacarpophalangeal and interphalangeal joints. Histopathologic examination revealed orthohyperkeratosis within focal clavus-like depressions of the epidermis and prominent hypergranulosis. There was no evidence of alterations in elastic tissue. The clinicopathologic distinction between focal acral hyperkeratosis and acrokeratoelastoidosis is blurred. There is enough evidence to consider the former as a histologic variant of Costa acrokeratoelastoidosis syndrome, and a better nomenclature for this disorder would be "acrokeratoelastoidosis without elastorrhexis."