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 Neisseria meningitidis . 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. CT showed widespread lymphadenopathy, hepatosplenomegaly and multilevel thoracic vertebral collapse. A bone marrow biopsy revealed a lymphoplasmacytic infiltrate and a lymph node biopsy showed features of nodal marginal zone lymphoma with plasmacytic differentiation.