Subcutaneous extensor tendon rupture associated with calcium pyrophosphate dihydrate crystal deposition disease of the wrist.

We report a patient with rupture of the ring extensor tendon associated with calcium pyrophosphate dihydrate crystal deposition disease of the wrist. Crystal deposits were noted in synovium and the triangular fibrocartilage complex. Histological examination revealed chronic synovitis with foreign body giant cell reaction to crystals. The cause of the tendon rupture was synovitis due to crystal deposition.