A 68-year-old male who had owned a bicycle shop for several decades visited our institute in March 2004 with a one-month history of swelling and pain of the right distal forearm. His dominant hand was right. On physical examination, an elastic soft mass, measuring 6 cmx4 cm, was observed on the palmar side of the right forearm. Motion of each finger was normal, but the range of motion of the wrist joint was slightly restricted. Skin color change and local heat were not observed around the mass. Laboratory data, including rheumatoid factor and C-reactive protein, were not contributory. He had no history of tuberculosis, and his tuberculin reaction on admission to the hospital was weakly positive. No hilar lymphoadenopathy was observed on a chest radiogram.
Plain radiograms of the right wrist and hand showed degenerative changes and Heberden's nodes in the distal interphalangeal joints, but no apparent calcification was observed in the mass (Figure 1). On magnetic resonance (MR) imaging, T1-weighted images showed a low-intensity mass surrounding the flexor tendons (Figure 2A). On T2-weighed images, the mass partially showed high-signal intensity (Figure 2B). Sagittal T2-weighed images demonstrated an effusion in the sheaths of the flexor tendons and many small low-intensity bodies in the mass (Figure 2C). The mass was moderately enhanced by administration of intravenous gadolinium (Figure 2D), but the small bodies were not enhanced.
An incisional biopsy was performed in June 2004. The mass existed adjacent to the flexor tendons and was encapsulated by a yellow fibrous wall. Many rice bodies had erupted from a small hole in the wall of the mass (Figure 3). Histological findings revealed hyperplastic tenosynovitis with fibrinous loose bodies (Figure 4). During the surgery, we confirmed that the flexor tendons were intact. In July 2004, he complained of disability to flex in his ring and little fingers. After physical examinations, we made a diagnosis of spontaneous rupture of the flexor tendons. An open repair was performed in August 2004. During the surgery, we observed granulation tissues proliferating around the flexor tendons (Figure 5) and a rupture of the flexor tendons of the ring and little fingers. The granulation tissues were removed, and the superficial flexor tendon was transferred to the ring finger. Tendon graft of the palmaris longus to the little finger was also performed. Histologically, the granulation tissues showed chronic synovitis (Figure 6), and acid-fast bacilli were negative. There was no apparent granuloma suggesting of sarcoidosis. The patient regained good function of the operated ring and little fingers with no evidence of recurrence at the latest follow-up in March 2009.