Bacterial monarthritis due to Neisseria meningitidis in systemic lupus erythematosus.

Two patients with systemic lupus erythematosus developed monarticular infectious arthritis, in which Neisseria meningitidis was recovered from knee synovial fluid. In one instance, the sole manifestation of meningococcal disease was a chronic, indolent, erosive monarthritis. In the second, a febrile, bacteremic illness presented with an acute, septic arthritis.