To the Editor.—
A fit, red-haired, 19-year-old man was referred to me by a general physician because of a two-year history of asymptomatic swelling around the proximal interphalangeal joints of the fingers. He had no family history of similar trouble. The hemoglobin value, complete blood cell count, sedimentation rate, and x-ray films of the chest, hands, and skull were normal.Complete general examination showed no abnormality apart from diffuse swelling over the dorsal aspect and sides of the proximal interphalangeal joints of the index, middle, and ring fingers (Figure). The affected skin was freely mobile, and the thumbs and toes were normal. A skin biopsy specimen from the medial side of the left middle finger near to the proximal interphalangeal joint showed hyperkeratosis and acanthosis overlying a dermis containing increased amounts of fibrous tissue (T.W. Stewart, MB, performed the histologic studies).True knuckle pads are rare, well-defined lesions of unknown