Aquagenic wrinkling of the palms (AWP) is an uncommon disease characterized by the rapid and transient formation of edematous whitish plaques on the palms on exposure to water. Although this disease is occasionally accompanied by hyperhidrosis, the pathophysiology of AWP remains unknown. Herein we describe a patient with AWP. The location of wrinkling was limited to the areas positive for iodine-starch test after water exposure, which suggests that AWP is etiologically related to hyperhidrosis. Histologic examination revealed hyperplastic and papillated eccrine glandular epithelium with the enlarged diameter of eccrine coils. Immunohistochemically, while aquaporin 5 (AQP5), one of the water channel AQP families, was present exclusively in the dark cells of sweat glands of healthy donors, an aberrant AQP5 staining, extending to the clear cells, was found in the patient with AWP. The hyperplastic glandular epithelium and aberrant AQP5 staining in the patient's sweat glands suggest that AWP stems from dysregulation of sweating.