Fulminant meningococcal infections in a family with inherited deficiency of properdin.

Three males in a large kindred died of meningococcal infections. In the index patient, properdin (P) was not detectable in serum. Two healthy males with a selective P deficiency were found in the family. There was no general susceptibility to infections, nor to other diseases as suggested by the family history. The serum bactericidal activity for Neisseria meningitidis group C, isolated from the index patient, was moderately reduced in P deficient serum, and was improved by addition of purified P.