Circumscribed palmar hypokeratosis: two cases and a review of the literature.

A 60-year-old female and a 59-year-old male each presented with a solitary circumscribed patch of depressed skin of the right thenar palm and right sole, respectively. Both lesions were present for approximately 30 years without a history of trauma or other inciting incident. Histologically, the lesions showed a well-demarcated abrupt decrease in the thickness of the stratum corneum with a central area of thinned stratum corneum and hypogranulosis. Inflammation was absent. Ultrastructurally, keratin filaments were evident in the stratum corneum, and a diminished granular cell layer was apparent. There was a decrease in maturation of the keratinocytes, however, no defects in corneodesmosomes or other ultrastructural components were identified. No evidence of human papilloma virus was detected by in situ hybridization studies. Based on these 2 cases and the 25 cases reported in the literature to date, this entity seems to represent a chronic localized non-inflammatory defect in keratinization on acral sites.