PARTIAL PROPERDIN DEFICIENCY IN A FRENCH FAMILY

Properdin is one of the regulatory proteins of the alternative pathway of the complement system. Human properdin deficiency is an X-linked d isorder strongly predisposing to meningococcal disease. Total deficien cy (type I), partial deficiency (type II), and deficiency due to a dys functionnal molecule (type III) can be differentiated immunochemically . Four males in a family showed a selective partial deficiency of prop erdin. These individuals had 10% of normal properdin concentration in plasma, as measured by ELISA, while the other complement components we re normal. Two of the properdin-deficient individuals in two generatio ns had meningococcal infections, Two were clinically healthy at the ti me of investigation. Measurement of plasma levels of properdin has to be performed in the case of Neisseria meningitidis, especially where t here is a previous history of severe bacterial infections in the same family as measurement of CH50 activity is ineffective for screening pr operdin deficiency.