Pachydermodactyly: a forme fruste of knuckle pads?

A 16-year-old boy presented with painless swellings localized to the radial and ulnar aspects of his second through to the fifth fingers on the left hand, with more subtle changes affecting two fingers on the opposite hand. This had developed in the absence of mechanical trauma. Investigations for an arthropathy were negative, while a biopsy showed marked epidermal hyperplasia and an expanded dermis. These features are typical of pachydermodactyly, a benign dermatosis of uncertain aetiology. The interesting feature of this case is the presence of knuckle pads in the father of the patient, which raises the possibility that these two similar entities are related.