Polyarticular arthritis secondary to Mycobacterium bovis infection: an unusual clinical presentation

We describe a 37-year-old Mexican man with incapacitating polyarticular arthritis secondary to Mycobacterium bovis infection. A dermatologist diagnosed psoriasis two years before admission. One year later due to symmetric ankle and knee arthritis, he was treated with three doses of etanercept. The arthritis extended to the carpus and metacarpophalangeal joints. Multifocal dactylitis and a left ankle periarticular abscess were documented. Concomitantly he developed fever, cough, and adenopathies. Ankle MRI showed osteomyelitis of the calcaneous with a posterior abscess. A CT-body scan documented mild pleural effusion that corresponded to an exudate. An ankle aspiration yielded a caseous fluid with acid-fast bacilli. Knee and ankle synovial biopsies documented a granulomatous synovitis. A lymph node biopsy showed granulomas with caseous necrosis. After 1 month, Mycobacterium bovis was isolated from these tissues. Antituberculous regimen was started with satisfactory response. Although largely eradicated, bovine tuberculosis still occurs. Nevertheless, the clinical presentation as polyarthritis is very uncommon and represents a diagnostic challenge.