Primary meningococcal arthritis as a presentation of nodal marginal zone lymphoma.

A 68-year-old man presented with a 4-day history of worsening knee and arm pain. On examination, there was erythema and swelling of the left knee and both wrists. Joint aspiration grew Blood tests showed an unusually high total protein level (100 g/L) and an IgM kappa paraprotein band of 45 g/L on protein electrophoresis.