Bursal osteochondromatosis of the shoulder: An exceptional location

IntroductionThe osteochondromatosis is a rare synovial tissue metaplasia. The location at the shoulder is very rare. Bursal affection is exceptional.Case presentationWe report a case of a male, 41 years old living in north Morocco and presenting to the rheumatology outpatient clinic at Fes Hassan II University Hospital with a swelling of the right shoulder that had been evolving for two years, without any history of trauma, gradually increasing in size, without fever or alteration of the general state. Clinical examination revealed a 5 cm soft, non-tender oval mass on the anterior surface of the right shoulder with no signs of inflammation but limited range of motion. Plain X-ray was normal and diagnostic ultrasonography revealed an avascular multilocular cystic mass. A differential diagnosis was considered and other conditions with comparable pictures were ruled out. The diagnosis was confirmed by a magnetic resonance imaging showing synovitis and distension of the sub acromiodeltoid bursa with many rounded bodies, few millimeters in size of intermediate signal in T1 and T2 without enhancement after intravenous gadolinium. A diagnosis of osteochondromatosis of the subacromiodeltoid bursa (third stage) was made. The patient underwent an open bursectomy and histological examination further verified the diagnosis.ConclusionPresenting such rare cases could help in raising the awareness of rheumatologists regarding such conditions when considering a differential diagnosis for patients presenting with monoarticluar shoulder swelling. Excision of the tumor has a remarkably better prognosis.