[Partial properdin deficiency revealed by a septicemia caused by Neisseria meningitidis].

Properdin is one of the regulatory proteins of the alternative pathway of the complement system. Human properdin deficiency is an X-linked disorder strongly predisposing to meningococcal disease. Total deficiency (type I), partial deficiency (type II), and deficiency due to a dysfunctional molecule (type III) can be differentiated immunochemically. Four males in a family showed a selective partial deficiency of properdin. These individuals had 10% of normal properdin concentration in plasma, as measured by ELISA, while the other complement components were normal. Two of the properdin-deficient individuals in two generations had meningococcal infections. Two were clinically healthy at the time of investigation. Measurement of plasma levels of properdin has to be performed in the case of Neisseria meningitidis, especially where there is a previous history of severe bacterial infections in the same family as measurement of CH50 activity is ineffective for screening properdin deficiency.