A 26-year-old woman was diagnosed with systemic lupus erythematosus in 2002 and was treated with prednisolone, mycophenolate, and hydroxychloroquine. In September 2013, she was admitted with nephrotic-range proteinuria. Renal biopsy confirmed class IV lupus nephritis. After failure of treatment with mycophenolate mofetil, enalapril, and high doses of steroids, she received two 1000-mg doses of rituximab one month apart. Prior to receiving rituximab, a chest x-ray showed normal findings, but a tuberculin skin test (TST) was not performed. A pre-employment TST performed in 2010 showed negative findings. Following rituximab she was maintained on 10-15 mg prednisolone daily. Four months after the second dose of rituximab, she presented with fever as well as pain and swelling in her right knee and left elbow. Her temperature was 39  C and erythrocyte sedimentation rate was 117 mm/hr. Gram stains and culture of aspirates from the knee and elbow joints yielded negative results for bacteria, as did a blood culture. A combination of methylprednisolone and intravenous ceftriaxone was given for a possible flare of lupus. Her condition improved, and she was discharged home. Two weeks later, she presented with similar symptoms accompanied by cough and shortness of breath. The patient's temperature was 38.3  C. Both her right knee and left elbow joints were erythematous and tender; her other joints were normal.
The anti-nuclear antibody titre was 1:2560 (normal <1:40); anti-double-stranded DNA level, 110 IU/mL (normal: 0-200); creatinine, 57 mumol/L; serum calcium, 2.63 mmol/L (normal: 2.06-2.44); and vitamin D, 43.6 nmol/L (optimal >=75). A plain x-ray of the left elbow showed cranial displacement of a proximal fractured fragment of the olecranon process with intra-articular extension associated with swelling of the olecranon bursa (Fig. 1A). Magnetic resonance imaging scan (MRI)of left elbow joint showing avulsion fracture involving the olecranon process (White arrow) with possible underlying osteomyelitis of the avulsed fragment in addition to synovitis and reactive bursitis of the left elbow joint (Fig. 1B).
MRI of the right knee joint revealed arthritis with synovial thickening, rice pad in the suprapatellar pouch, and large lateral femoral condyle erosion in addition to severe bone marrow edema involving almost the entire lateral femoral condyle. MRI findings were highly suggestive of tuberculous arthritis (Fig. 2). A computed tomography (CT)-guided biopsy confirmed acute-on-chronic osteomyelitis of the right knee. A synovial fluid smear yielded positive results for acid-fast bacilli, and culture confirmed MTB.
An initial chest radiograph was reported as normal; conversely, a CT scan of the chest showed marked miliary nodular shadowing consistent with miliary tuberculosis (Fig. 3). Sputum smear yielded negative findings for acid-fast bacilli; however, sputum polymerase chain reaction (PCR) test using a GeneXpert system (Cepheid, Sunnyvale, CA, USA) yielded positive results for MTB. The gene mutation for rifampicin resistance was not detected. A fully sensitive MTB was isolated from both the sputum and synovial fluid culture.