Complement deficiencies in selected groups of patients with meningococcal disease.

We have examined 125 individuals who have earlier had meningococcal (mgc) disease. They belonged to one or more of the following groups: (1) 2 or more cases of mgc disease in the same family; (2) individuals with 2 episodes of mgc disease or with 1 episode of mgc disease and 1 or more episodes of purulent meningitis of another aetiology; and (3) infections with Neisseria meningitidis belonging to serogroups that are uncommon as causes of disease and presumably low-virulent (W-135, 29E, X, Y). Among these we found 15 complement (C)-deficient individuals (12%). The prevalence of C deficiency in the groups above was 7%, 41% and 19%, respectively. The first group (family cases), is very heterogeneous and may be further subdivided into 2 groups: families whose members fell ill within an interval of 30 days (in these the prevalence of C deficiency was 2%), and families in which the interval between mgc disease cases exceeded 30 days (in those the prevalence of C deficiency was 14%). We found a predominance of defects of the initiation pathways, with properdin deficiency being the most common.