Tuberculous arthritis in children. Diagnosis by needle biopsy of the synovium.

In two children ages 8 months and 4 years, tuberculous synovitis of the knee was suggested by pathologic examination of synovial tissue obtained through needle biopsy. Culture of the biopsy material was positive for Mycobacterium tuberculosis in one case. In this child, the tuberculin test was negative, in the absence of anergy, at the time the child was first evaluated, and the primary lung lesion was not identified by the radiologist. Tuberculous synovitis has not previously been recognized as part of primary tuberculosis during the early weeks when the tuberculin skin test may be negative. Magnetic resonance imaging (MRI) is a sensitive modality for demonstrating joint fluid, synovial hypertrophy, and associated osteomyelitis, if present. With the increasing frequency of cases of tuberculosis in the population, greater awareness of the risk of tuberculous arthritis in childhood is important in order to recognize this unusual presentation. If negative early on, the tuberculin skin test should be repeated after 6 weeks of arthritis. A needle biopsy of the synovium is helpful and appropriate in all children with monoarticular arthritis who have a positive tuberculin skin test.