Tubercular monoarthritis of the glenohumeral joint in a non-endemic region: Vancouver, Canada

Since immigrating to Canada he made several return trips to India including a 1 month period in 2019. Physical examination and history are often not enough to make the diagnosis.2 Useful diagnostic tests include radiographs of affected and contralateral joint, synovial fluid analysis for culture, gram stain, crystals and cell count.2–7 Gout and bacterial septic arthritis response to initial treatment can be diagnostic.2 3 Serum inflammatory markers such as ESR and CRP are non-specific and not helpful differentiators.4 Synovial fluid smear sensitivity for acid-fast bacilli in true cases of tubercular arthritis is low (20%–40%),5 requiring a high index of suspicion and usually a synovial tissue biopsy for diagnosis. Very occasionally, the TB arthritis is oligoarticular causing diagnostic confusion with other inflammatory arthritis.5 10 The differential diagnosis of acute monarthritis in a TB endemic region, such as India for example, is similar to North America with septic arthritis and gout being the most common diagnoses.5 8 11 However, in subacute or chronic monarthritis, the most common causes are TB, fungal infections, followed then by autoimmune conditions rheumatoid arthritis, spondyloarthropathies and reactive arthritis.5 11 Learning points Mycobacterium tuberculosis should be included in any differential diagnosis of monarthritis even in non-endemic regions when your patient has epidemiologic risk factors until a definitive diagnosis is made.