Rice body synovitis of the shoulder joint: a case report and review of clinical management and pathology.

Background: Rice body synovitis is a rare subtype of synovitis, often secondary to chronic inflammatory diseases, such as rheumatoid arthritis (RA). Due to its non-specific clinical manifestations, it is prone to misdiagnosis. Methods: This report describes a 58-year-old male patient with left shoulder rice body synovitis. The patient had a 25-year history of rheumatoid arthritis and presented with a left shoulder mass for over 2 months, accompanied by pain and limited joint mobility within the previous week. Laboratory findings revealed markedly elevated rheumatoid factor levels (128.0 IU/mL) and anti-cyclic citrullinated peptide antibody levels (86.0 RU/mL), along with an elevated erythrocyte sedimentation rate (62.25 mm/h) and C-reactive protein level (15 mg/L), all of which, being above normal reference ranges, indicated active rheumatoid arthritis. An MRI showed marked capsular and bursal distension with multiple well-defined rice body-like nodules measuring approximately 0.5-0.8 cm. These nodules had low-to-intermediate signal intensity within a hyperintense effusion, producing the characteristic "floating lotus sign." After contrast administration, the thickened synovium was enhanced, whereas the nodules showed no obvious enhancement. Results: The patient underwent arthroscopic exploration and debridement. Intraoperatively, multiple rice-grain-like bodies and proliferative synovial tissue were completely removed, followed by rotator cuff repair. Postoperative pathology revealed loose bodies composed of an amorphous necrotic core surrounded by fibrin, consistent with the pathological changes of rice body synovitis. Postoperative management included analgesic treatment, staged shoulder rehabilitation, and rheumatology follow-up for reassessment of RA activity and optimization of disease-modifying antirheumatic drug (DMARD) therapy. At the 6-month follow-up, the patient's pain had resolved, and his shoulder's range of motion had returned to normal (180° abduction, 160° elevation). Imaging follow-up showed no recurrence. Conclusion: This single case suggests that RA-associated rice body synovitis should be considered when patients with chronic inflammatory arthritis present with persistent shoulder swelling and typical MRI findings. Arthroscopy can be diagnostically and therapeutically useful, but favorable short-term outcomes cannot be generalized from one case. Long-term follow-up and optimized RA/DMARD management remain necessary to reduce recurrence risk.