Absence of the seventh component of complement in a patient with chronic meningococcemia presenting as vasculitis.

A previously healthy 40-year-old man presenting with fever, arthritis, and cutaneous vasculitis was found to have chronic meningococcemia. Evaluation of his complement system showed an absence of functional and antigenic C7, compatible with a complete deficiency of the seventh component of complement. Study of the patient's family spanning four generations showed heterozygous deficiency of C7 in five members. Chronic neisserial infection can be associated with C7 deficiency and must be distinguished from other causes of cutaneous vasculitis.