Poncet’s Disease Presenting as Polyarthritis with Erythema Nodosum in a Child: A Case Report

Abstract Background: Poncet’s disease, also known as tuberculous rheumatism, is a rare immune-mediated, nonerosive mono- or poly-arthritis associated with tuberculosis (TB) at an extra-articular site, without direct mycobacterial invasion of the joints. Pediatric cases are rare. Clinical Description: A 6-year-old girl presented with painful erythematous nodules over the lower limbs, followed by intermittent fever and tender swellings involving the knees and elbows, with no other constitutional symptoms, weight loss or anorexia. Examination confirmed erythema nodosum and restricted joint movements without effusion or deformity. Management and Outcome: Laboratory evaluation showed raised total leukocyte counts and elevated inflammatory markers with negative autoimmune markers. Ultrasound showed minimal synovial thickening of both knees and the right elbow, without effusion. Following a lack of response to antibiotics and sterile blood cultures, a chest X-ray was done, which showed left middle-zone opacity, confirmed as consolidation by computed tomography. Mantoux positivity in the face of such pulmonary findings and erythema nodosum made TB the most likely diagnosis. Antitubercular therapy (ATT) was started, followed by rapid and complete resolution of joint symptoms and skin lesions within 6 weeks. The arthritis was thus attributed to reactive tubercular rheumatism or Poncet’s disease. Conclusion: Poncet’s disease should be considered in children presenting with arthritis, not responding to conventional antibiotics, especially in TB-endemic regions. Early recognition of extra-articular TB and prompt initiation of ATT may result in rapid recovery, thus confirming Pnset’s disease.