Heterozygous C8beta complement deficiency does not predispose to meningococcal disease.

We have identified 42 Russian patients with homozygous C8beta complement component deficiency, all of whom had experienced at least one episode of systemic meningococcal disease. About 90% of these individuals have a C --> T exchange in exon 9, leading to a premature stop codon. If, like the homozygous-deficient state, heterozygous C8beta deficiency constitutes a risk factor for meningococcal disease, it would be expected to be detected with increased frequency among individuals suffering from this disease. Using allele-specific polymerase chain reaction (PCR), we studied 153 consecutive patients with meningococcal disease admitted to the Moscow Hospital for Infectious Diseases to determine the frequency of C8 null allele. No individuals with heterozygous C --> T exchange were identified among these 153 patients, despite the fact that seven persons were detected who had homozygous C8beta deficiency, caused by the same C --> T exchange in exon 9, and one patient who had C7 component deficiency. Thus, heterozygous deficiency, although more frequent than homozygous deficiency in the general population, does not result in a substantial increase in susceptibility to meningococcal disease.