Pachydermodactyly.

Pachydermodactyly is a rare distinct form of fibromatosis characterized by dense fibrosis and fibroblastic proliferation around one or more proximal interphalangeal joints. Pachydermodactyly affects the appositional and dorsal aspects of proximal digits II-V. The lateral aspects of the index fingers, the medial aspect of the fifth digits, and the thumbs are usually unaffected. A typical patient was a young adult man with a long history of idiopathic asymptomatic swelling in the fingers. Skin biopsy specimens obtained from three patients with pachydermodactyly showed marked thickening of the dermis with extension of collagenous fibers into the subcutaneous tissues. There was poor demarcation between the papillary and reticular dermis. The cytology of the fibroblasts appeared benign. Isolation of collagen from the involved sites revealed collagen Types I, III, and V in a pattern typical of fibromatoses; i.e. increased Types III and V. Compared with the collagen profile of normal reticular dermis, increased numbers of fine-diameter collagen fibers were notable in electron micrographs.