Old enemy on a difficult terrain: tuberculosis in rheumatology practice with focus on uncommon extrapulmonary affection

One third of all cases of tuberculosis (TB) are extrapulmonary (EP) and less than 5% of these are associated with musculoskeletal (MSK) system. TB can infect MSK at several sites (spinal/axial and extra-axial/peripheral) and present with multifocal damage. Inflammatory rheumatologic disorders and immunosuppressive therapy may further compound the problem. A high index of suspicion is required. Modern imaging and microbiology-serology techniques provide early diagnosis with improved prognosis. All this was demonstrated by a retrospective analysis of case records of 23,651 patients examined in a single rheumatology center in Pune during the period 2005–2009. The study used the patient referral database to retrieve data and perform analysis. Thirty-five percent of the total cases were classified as rheumatoid arthritis (RA). Ninety-eight cases recorded TB in the case record either as a past illness or primary illness, or concurrent complication. 0.4 percent cases of RA developed TB which was predominantly pulmonary. TB affected MSK in 16 cases (0.07%) with 12 cases suspected of Poncet's disease. Two cases (1 with RA) were diagnosed as multifocal (with non-contiguous spinal disease, psoas abscess). One case each of tubercular infection of the breast and wrist (both rare forms) was associated with inflammatory arthritis. One case each of primary MSK tubercular infection of wrist extensor tenosynovitis and monoarticular knee synovitis was also recorded. TB lymphadenopathy was the commonest manifestation of extrapulmonary tuberculosis (EPTB). Though infrequent, TB remains an important differential diagnosis in rheumatology setting.