[Osteoarticular tuberculosis: a differential diagnosis of idiopathic juvenile arthritis]

We report a case of extrapulmonary tuberculosis with oligoarthritis and synovitis in a 6-year-old girl with undiagnosed disseminated tuberculosis.

The child, adopted from Ethiopia, was admitted to the pediatric rheumatology unit for suspected idiopathic juvenile arthritis. She presented with clinical signs of subacute arthritis of the right knee. Joint symptoms began insidiously and followed a short period of fever and pain in the right hip. Clinical examination showed voluminous cervical lymphadenitis, night sweats, and a moderate alteration of the child's general condition. The medical history revealed that since her arrival in France, 2 years before, she had had febrile subacute pneumonia. A review of the chest x-ray diagnosed primary pulmonary tuberculosis. An intradermal tuberculin test confirmed the diagnosis with a phlyctenular response and a diameter exceeding 20mm. Additional evaluation showed cervical lymphadenitis and intense synovitis of the right hip and knee joints. With an appropriate antitubercular regimen, her condition improved within a few months. After 1 year of treatment, magnetic resonance imaging (MRI) showed normalization of the impaired joints with no functional sequelae.

Although the spine is a common target for osteoarticular tuberculosis (OAT), peripheral involvement in this case underlines the polymorphism of OAT in children. It illustrates a case of OAT strictly located to the synovial membranes, which usually occurs in one-third of OAT cases. In addition, MRI showed tenosynovitis of the quadriceps. The child presented with unilateral oligoarthritis instead of chronic insidious monoarthritis or symmetrical oligoarthritis as usually described in pediatric OAT. When available, MRI is the best way to evaluate OAT lesions. Mycobacterium tuberculosis can be isolated from sputum, gastric aspiration, and joint fluid or synovial biopsy. Histological lesions can reveal advanced tuberculosis with the presence of caseous follicular lesions. Rapid bacterial detection using polymerase chain reaction remains insufficiently useful in those situations. The recommended therapeutic regimen consists of 3 months with four antitubercular agents (rifampicin, isoniazid, pyrazinamide, and ethambutol) followed by 9 months of a dual therapy (isoniazid, rifampicin).