Primary meningococcal arthritis.

Arthritis in meningococcal disease is not uncommon and can be caused by either septic invasion of joints or allergic manifestations. Primary meningococcal arthritis (PMA) is, on the other hand, a rare form of meningococcal disease presenting as an isolated septic arthritis without other signs of meningococcal disease. We describe here the first two cases of PMA reported from Scandinavia. The patients were males, 3 and 47 years old, both with arthritis in an ankle joint. PMA is most commonly seen among male infants. Large joints, mainly knee joints, are most often involved and not seldom is the disease polyarthritic. PMA may appear with a previous or on-going upper respiratory tract infection and/or a maculopapular skin rash. If properly treated the prognosis is good.