[Primary meningococcal-monoarthritis (Neisseria meningitidis serotype C) in a child].

A 26-month-old girl had a painful, swollen right knee, accompanied by fever and vomiting. She had had an upper respiratory tract infection for a number of days. Following a positive culture of synovial fluid, monoarthritis caused by Neisseria meningitidis serotype C without other signs of illness was diagnosed. She recovered completely after one joint aspiration and intravenous and oral antibiotic therapy. N. meningitidis serotype C infections without meningitis or septicaemia are rare, but should form part of the differential diagnosis of septic monoarthritis.