Rupture of the Achilles tendon in rheumatoid arthritis with histologic evidence of enthesitis. A case report.

Spontaneous Achilles tendon rupture occurred in a 60-year-old man with a two-year history of sero-positive rheumatoid arthritis (RA). Histologic section of the ruptured Achilles tendon revealed the existence of rheumatoid granulation that consisted of lymphocytes, histiocytes, and small vascular proliferation within the tendon tissue. The enthesis of the tendon to the calcaneus also revealed lymphocyte infiltration in the bone marrow and rheumatoid granulation within the tendon. Throughout the course of his disease, the patient had not been treated with corticosteroids. These facts suggested that enthesis (attachment of tendon to bone) was one of the extraarticular sites of the rheumatoid inflammation and that enthesitis was a possible cause of Achilles tendon rupture in this RA patient.