Circumscribed acral hypokeratosis (CAH, also called circumscribed palmar or plantar hypokeratosis) is an idiopathic benign condition seen most commonly in women between the ages of 40 and 80 years. However, a few cases of congenital CAH have been reported in children.

CAH classically presents as a solitary circumscribed, depressed, erythematous plaque on the palm or sole, although cases with multiple lesions have been described. The dominant hand is most frequently affected, specifically the thenar or hypothenar region. Less common locations include the fingertips and medial soles. CAH is typically asymptomatic, but tenderness and burning have occasionally been reported.

CAH usually remains consistent in size, shape, and color over time. Spontaneous resolution has been reported in several cases. There has been one report of an actinic keratosis developing within a lesion of CAH.

The pathophysiology is unclear, but recent immunohistochemical findings have shown abnormal cytokeratin expression in CAH lesions. This discovery, along with the reports of congenital lesions, may indicate that CAH occurs as a result of abnormal epidermal keratinization.