Case 1

A 66 year old woman noticed a firm nodule on the volar apect of the proximal phalanx of the left index finger. She had first noticed it 12 months previously and had watched it progressively increase in size to a diameter of five millimetres. On clinical grounds, it was thought to be a dermoid cyst. She had a history of an undifferentiated connective tissue disease with recurrent Raynaud's phenomenon, swollen fingers, a positive antinuclear antibody titre of 1:40 with an homogeneous pattern. Antibodies to extractable nuclear antigens and double stranded DNA were unable to be detected. Her other medical problems included lumbar spondylosis and osteoarthritis of the knees. Plain radiographs revealed chondrocalcinosis in the left wrist triangular fibrocartilage (see fig 1) but no calcification was noted in the nodule. Serum calcium and iron studies were normal.

As the lesion was causing some inconvenience, it was excised. At operation, a well encapsulated calcific nodule situated intradermally and extending to, but not involving the flexor tendon sheath, was excised.

On examination under polarised light, the nodule consisted of weakly positively birefringent crystals with the typical morphological characteristics of calcium pyrophosphate (CPPD). The crystals were extensively deposited in fibrous tissue with only a small inflammatory infiltrate.