A 23-year-old previously healthy woman had pain in the right knee and both ankle joints, which had been present for approximately five days. She had no other significant medical history. Laboratory tests results for rheumatoid factor and anti-cyclic citrullinated peptide antibodies were negative. Approximately two weeks later, an extensive erythema nodosum developed over her over lower limb (Figure 1). She also had a single, non-tender, 2 × 3 mm supraclavicular lymph node.
Histopathologic examination of an excised lymph node biopsy specimen showed extensive areas of caeseation with epitheliod granulomas, and Langhans and foreign body giant cells, which led to a diagnosis of tuberculous lymphadenitis (Figures 2 and 3). Mycobacterium tuberculosis was grown grew from a culture of the lymph node. The lymph node excision site did not heal properly (Figure 4). The patient was treated with ethambutol, pyrazinamide, isoniazide, and rifampicin. She responded dramatically and was completely symptom free after one month of therapy with no need for any pain relievers.
Poncet’s disease is synonymous with reactive arthritis that develops in the presence of active tuberculosis,1 although a synovial biopsy is required to definitively rule out actual infectious tuberculous arthritis. Poncet’s disease and erythema nodosum may be different expressions of similar immunopathologic mechanisms.2
Address correspondence to Ankit Shrivastav, R-235, Junior Doctors Hostel, Department of Internal Medicine, Institute of Post Graduate Medical Education and Research, 242 AJC Bose Road, Kolkata 700020, Kolkata, India. E-mail: