Tuberculous Arthritis Mimics as RA in Patient With Lupus Nephritis: Case Report

Tuberculosis is a relatively common infectious disease and has remained a significant health problem throughout the world. The symptoms of tuberculosis could be atypical and non-specific, especially in immunosuppressed patients. While patients with systemic lupus erythematosus (SLE) are at higher risk of developing an opportunistic infection (including tuberculosis), isolated tuberculous arthritis of the ankle joint is rare.

Dr Mohd N bin Ismail and Dr Siti M Ab Rahim reported a 45-year-old woman presented with pain and swelling over her left ankle and right wrist joint for the previous 4months. The swelling progressively increased in size and was associated with morning stiffness. The patient denied fever, cough, or other systemic symptoms and had no contact with a tuberculosis patient. She had a history of hypertension, uterine fibroid and class IV lupus nephritis and she was on regular diltiazem, azathioprine, hydroxychloroquine, prednisolone, alfacalcidol and losartan. Besides, she had taken mycophenolate mofetil tablets for 1year as the immunosuppressive agent for her lupus nephritis 2years previously.

Upon physical examination, the physicians observed swelling in the left ankle joint measuring 6×8 cm, right wrist and second to the fifth metacarpophalangeal joint over the right hand. Ultrasound revealed left foot synovial hypertrophy, with calcification within, as well as severe structural deformity and evidence of active synovitis. Physicians also noted joint erosion and effusion over the right second to fifth metacarpophalangeal joint and bilateral wrist joints. Laboratory tests revealed a white cell count of 11.7×109/L, C-reactive protein of 31.4 mg/L, erythrocyte sedimentation rate of 48 mm/hour and normal renal and liver function tests.

Given her clinical presentation, the physicians diagnosed her with RA and treated her with methotrexate 15 mg/week. However, they found no improvement in the left ankle after 4months of methotrexate therapy. The MRI of the left ankle confirmed the joint effusions with synovial proliferation, especially in the intercarpal, carpal-metacarpal, and subtalar joints, with thickened synovium and extensive bone erosions. Due to poor response to anti-inflammatory drugs and negative ACPA, physicians reviewed their initial diagnosis. They aspirated 10cc of greenish, cloudy fluid from the left ankle. Upon analysing the synovial fluid, they noted neutrophils in the background of granular debris, suggestive of acute suppurative inflammation. Empiric treatment for septic arthritis with cefazolin was initiated. Tuberculin skin test showed a strong positive result. After 5days on antibiotics, the bacterial culture showed no growth, but the molecular tuberculosis genome test turned out to be positive for Mycobacterium tuberculosis. So, she was treated with quadruple therapy of rifampicin, isoniazid, ethambutol and pyrazinamide for 2months, followed by a maintenance phase, comprising of isoniazid and rifampicin for 7months.

The patient completed the 9months of anti-tuberculosis drugs. The swelling markedly reduced in size; however, the left ankle deformity remains.

The authors concluded, "The diagnosis of tuberculous arthritis is difficult in patients with SLE as there are many overlapping features in between the two. In addition, the typical presentation of tuberculosis might not be present, especially in an immunocompromised patient. Hence, the diagnosis of TB should always be considered in cases with chronic arthritis especially in endemic area."