Sympathetic arthritis - A symptom of Chronic Recurrent Multifocal Osteomyelitis (CRMO)

The seemingly obsolete term ,,sympathetic" arthritis returns to the field of vision with growing experience on Chronic Recurrent Multifocal Osteomyelitis (CRMO). An analysis of mainly adolescent and adult cases of CRMO (n=36) showed inflammatory joint changes in 23 cases (64%), in 16 cases affecting the hip joint and in 18 cases affecting peripheral joints, of which 34 joint lesions were located in the neighbourhood of acetabular or metaphysical/epiphyseal locations of inflammation. The synovial inflammation was probably induced by bone inflammation in the neighbourhood as a concomitant symptom, possibly conducted by the periosteum and capsular structures of the joint. Sympathetic coxitis pertains to the ,,pelvic type" of CRMO, predominantly occurring in adolescents; affection of knee-, foot-, wrist-, tibio-fibular and finger-joints occur. No signs of enthesitis are found in MRI, different from cases of psoriatic arthritis with concomitant inflammatory joint lesions. ,,Sympathetic" CRMO-related arthritis has as good a prognosis as CRMO itself has, since it is supported by medication with acithromycine and calcitonin. Secondary arthrosis is rare.