Hereditary callosities with blisters

A family with calluses of the soles associated with blistering is described. Electron microscopic study of a bulla showed an intraepidermal blister with cytolysis of keratinocytes and clumping of tonofilaments. Review of the literature and our own experience with keratoderma palmaris et plantaris revealed no similar patients with this combination of findings. The appearance of the soles is similar to pachyonychia congenita, but the lack of nail and mucous membrane changes is not consistent with that disorder. Treatment with isotretinoin caused reduction in the size of the calluses but exacerbated the blistering.