A 55-year-old woman with rheumatoid arthritis treated with intravenous tocilizumab presents with an acutely painful, swollen knee. Her temperature is

Question

A 55-year-old woman with rheumatoid arthritis treated with intravenous tocilizumab presents with an acutely painful, swollen knee. Her temperature is 37.2°C, CRP 3 mg/L and peripheral white-cell count 6.5 × 10^9/L. Synovial fluid is turbid, with a white-cell count of 52,000/μL and 90% neutrophils; Gram-positive cocci are seen on Gram stain. Which statement best explains the discordant systemic and synovial findings and should guide assessment?

Accepted Answer

IL-6 receptor blockade can suppress CRP and systemic inflammatory features, so normal blood markers must not override clinical and synovial evidence of infection.

Answer

Peripheral white-cell count is unaffected by IL-6 receptor blockade and reliably excludes serious infection when normal.

Answer

Tocilizumab-associated neutropenia makes the synovial white-cell count unreliable, so crystal analysis should determine immediate management.

Answer

Normal CRP retains a high negative predictive value, so the Gram stain should be repeated before treating infection.

Answer

Tocilizumab reduces bacterial arthritis risk but increases sterile neutrophilic effusions, so observation pending culture is appropriate.

Masked Infection on Tocilizumab — SCE Rheumatology MCQ