Discussion of case
The 45-year-old female diagnosed with rheumatoid arthritis and diabetes was on regular DMARD and oral hypoglycemic agent therapy with a stable disease. She presented to the clinic with acute monoarthritis. The possible diagnosis to be considered is either exacerbation of RA or infective arthritis. Since the fever or local rise in temperature was absent, the possibility of bacterial infection can be excluded. The possibility of infective arthritis should be considered, since the patient was diabetic and the monoarthritis persist from last few days.
Other diagnostic possibilities are acute exacerbation of RA in single joint, injury and/or sprain. But the patient had no history suggestive of trauma, hence crystal arthropathies and other differentials are less likely.
The presence of very high CRP and ESR suggest a possibility of infection. Radiology was normal. Hence further investigation should focus on synovial fluid aspiration and conducting gram stain, AFB stain and if possible, PCR for tuberculosis. The patient being a diabetic, the clinical symptoms may not be florid.
The infective monoarthritis is a well-described complication of RA and its incidence is higher in diabetics.1 In the current patient, there was a co-existence of both the risk factors. In a study from US, septic arthritis was reported to be 14 times greater in RA patients than the control population.2 The incidence of infection is also higher in patients with diabetics and steroid users. The presence of infection associated with highly elevated CRP indicates the diagnosis as septic arthritis.
Final diagnosis
Septic arthritis in RA
Follow-up
The clinical investigation of aspirated fluid reported S. aureus, sensitive to amoxycillin and clavulanic acid. The patient was treated with the same antibiotics. Two days resting splint was provided. The joint function was completely restored with early antibiotic mobilization.
Learning points
- Septic arthritis should be considered in RA patients, especially if a severe flare of a single joint is noted.
- Total count and dramatically elevated CRP are the indicators of infection.
- Synovial fluid tapping and testing should be performed whenever even with slightest suspicion.
References
- Jean-Jacques D, Soubrier M, Suzie B. Pyogenic arthritis in adults. Joint Bone Spine. 2000; 67(1): 11–21.
- Doran MF, Crowson CS, Pond GR, O'Fallon WM, Gabriel SE. Frequency of infection in patients with rheumatoid arthritis compared with controls: a population-based study. Arthritis Rheum. 2002; 46(9): 2287–2293.
