A 42-year-old Sri Lankan-Sinhalese male presented with right knee joint swelling and pain for one year. Knee joint pain was associated with features of inflammatory arthritis in other small and large joints of the limbs. He experienced intermittent fever and progressive loss of weight for the same duration.
He was a patient with long-standing history of rheumatoid arthritis (RA) and interstitial lung disease. At the very first presentation to the rheumatology clinic, 26 peripheral joints were involved including all proximal interphalangeal (PIP) joints, metacarpophalangeal (MCP) joints, and both wrist joints. His joint symptoms persisted for 3-month duration. Though both rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) were negative, initial erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were elevated. Diagnosis of RA was initially made based on 2010-EULAR/ACR criteria in which his score was 7.
Current medications include methotrexate (MTX) 7.5 mg weekly, sulfasalazine (SSZ) 1 g thrice a day, leflunomide (LEF) 10 mg daily, and mycophenolate mofetil (MMF) 1 g twice a day. Despite good drug adherence, control of disease activity is poor during last two years with high disease activity score (DAS28 > 5). Hence, to achieve low disease activity, we planned for rituximab therapy which was not readily available in our resource-poor setting. Oral prednisolone has been prescribed intermittently to relieve his symptoms.
Examination revealed swollen and tender right knee joint with effusion and limited range of motion (Figure 1). Proximal interphalangeal, metacarpophalangeal, wrist, elbow, and shoulder joints were symmetrically involved with tenderness. Rest of the examination was unremarkable.
His ESR was persistently elevated above 50 mm/hr that was attributed to active synovitis. Other investigations were as follows: white blood cell count, 6600/mm3 with 72% neutrophils; platelet count, 480 000/mm3; hemoglobin, 12.0 g/dL; CRP, 14 mg/L; and serum uric acid, 6 mg/dL. Plain radiographs of right knee joint were normal except for soft tissue swelling (Figure 2). Ultrasonography of the knee showed joint effusion and marked synovial thickening.
During last one year, his right knee joint has been aspirated several times due to recurrent accumulation of joint fluids causing significant discomfort. The most recent (one month ago) findings of joint fluid analysis were as follows: polymorphs, 18240/mm3; lymphocytes, 60320/mm3; and red cells, nil/mm3. Routine bacteriology culture did not yield any organism in multiple occasions. Uric acid crystals or malignant cells were never identified on those samples. Before eight months of this presentation, the patient was treated with empirical intravenous antibiotics even for the suspected septic arthritis. Intra-articular steroid was injected to the right knee joint on two occasions afterwards.
During a routine clinic visit, we reconsidered the possibilities for resistant knee joint effusion and sent the joint fluid for acid fast bacilli (AFB) and polymerase chain reaction for TB (TB-PCR), and both came positive. He was immediately started on anti-tuberculous therapy upon diagnosis.
His respiratory problem was reevaluated with computed tomography (CT) of chest that further confirmed non-specific interstitial pneumonia (NSIP). The Mantoux test was non-reactive. AFB and TB-PCR on broncho-alveolar lavage (BAL) were negative. He was subjected to HIV screening test that also came negative.