RHE/WED/01 INFECTION WITH MYCOBACTERIUM KANSASII CAUSING CHRONIC MONOARTHRITIS OF THE ANKLE MIMICKING JUVENILE IDIOPATHIC ARTHRITIS

¹B Williams, ¹D Shingadia, ²R Scott-Jupp, ¹G Dixon, ¹P Brogan. ¹Great Ormond Street Hopsital, London, UK; ²Salisbury District Hospital, Salisbury, UK

Case: A case of a 5-year-old boy with a history of chronic relapsing monoarthritis of the left ankle, first presenting at 18 months is described. At presentation he was systemically well and blood inflammatory markers were not raised. Initial joint aspirate grew no organisms on culture, magnetic resonance imaging of the ankle with contrast demonstrated synovitis and a plain radiograph showed mild juxta-articular osteopenia with no joint erosions. He showed fleeting response to treatment with intra-articular steroid injections, oral prednisolone and no response to methotrexate. He re-presented 3.5 years into his illness with a 2-week history of increased ankle pain and swelling, fever and night sweats. Plain radiographs now revealed a lucent area in the distal tibia and talus. Quantiferon and Mantoux tests were positive. Open biopsy of the talus, tibia and synovium was performed and histology showed chronic granulomatous inflammatory infiltrates with areas of necrosis. Atypical mycobacteria grew from the aspirated fluid, which was revealed to be Mycobacterium kansasii by 16s ribosomal sequencing. Methotrexate was stopped and therapy with isoniazid, ethambutol, rifampicin and clarithromycin was started.

Discussion: M kansasii is an acid-fast bacillus typically presenting as a chronic pulmonary infection resembling tuberculosis in adults and is rarely seen in children. Septic arthritis caused by this organism is rare and is usually described in patients with underlying immunodeficiency. It is not readily isolated from environmental sources, with minimal evidence of person-to-person transmission. This patient lives in the New Forest and his garden is frequented by badgers, known to be an important animal reservoir for atypical mycobacteria. It was therefore speculated whether this was a zoonotic infection, or if the organism was introduced …