Musculoskeletal tuberculosis presenting as polyarthritis: a diagnostic challenge

Background: Polyarthritis in the elderly encompasses a broad range of differential diagnoses, including rheumatic diseases, infections, and malignancy. Case Description: A 72-year-old woman with a 2-year history of persistent, asymmetrical additive hand polyarthralgias, initially responsive to a short course of low-dose corticosteroids (5 mg), presented with polyarthritis involving the hands and wrists. She denied inflammatory back pain, skin lesions, or family history of psoriasis, and had no history of uveitis or gastrointestinal symptoms. Laboratory tests revealed iron-deficiency anemia, elevated inflammatory markers, and negative rheumatoid factor and anti-citrullinated protein antibodies. Screening for both active and latent tuberculosis was negative. Radiographs demonstrated bilateral radiocarpal joint space narrowing and osteoarthritic changes of the hand joints, and musculoskeletal ultrasound revealed tenosynovitis of the 5th and 6th extensor compartments of the right wrist. MRI confirmed inflammatory changes. Seven months later, the patient developed painful cutaneous lesions on the right forearm and wrist. CT imaging revealed enlarged axillary lymph nodes, and biopsy confirmed Mycobacterium tuberculosis infection. Anti-tuberculous therapy resulted in clinical improvement, normalization of inflammatory markers, and resolution of cutaneous lesions. Despite treatment, some degree of functional limitation persisted, particularly at the right wrist, likely reflecting the impact of diagnostic delay. Discussion/Conclusions: This case highlights the importance of considering infectious aetiologies, particularly tuberculosis, in elderly patients presenting with polyarthritis, especially in the absence of typical autoimmune markers. Early recognition and prompt treatment are essential to prevent complications and improve outcomes. Key Messages Musculoskeletal tuberculosis is a rare but important differential diagnosis in elderly patients presenting with polyarthritis. Tuberculosis may mimic inflammatory rheumatic diseases, particularly in seronegative cases, leading to diagnostic delay. Early recognition and appropriate treatment are essential to prevent irreversible joint damage and functional impairment.