Circumscribed palmar or plantar hypokeratosis: a distinctive epidermal malformation of the palms or soles.

Abstract

Epidermal malformations of the skin include a group of heterogeneous developmental defects that result from errors in morphogenesis of the epidermis during intrauterine life. The purpose of this study was to report the clinical and histopathologic features of a distinctive epidermal malformation involving the skin of the palms or soles. Ten patients were included in this study. All of them showed the same clinical features that consisted of a solitary circumscribed and circular area of erythematous depressed skin on the palm or on the sole. Diagnosis was confirmed by histopathologic study. All patients were middle aged or elderly. Nine patients were women and one was a man. The lesions showed predilection for the skin of the thenar and hypothenar regions of the palm or the medial side of the sole. Histopathologic study demonstrated a depression of the epidermis, with a sharp stair between normal and involved skin. The epidermis covering the depression showed markedly thinner horny layer and a slightly diminished granular cell layer when compared with adjacent noninvolved skin. Keratinocytes of the squamous cell layer, granular cells, and corneocytes showed, otherwise, a normal appearance. Serial sections failed to demonstrate cornoid lamellation. On the basis of the clinical and histopathologic findings in these 10 patients, we have named this malformation circumscribed palmar or plantar hypokeratosis. This lesion seems to be a distinctive entity that has not been previously described.