Congenital properdin deficiency and meningococcal infection.

We report a family in which three males in two generations had meningococcal infections; one of them died. Hemolytic activity of the alternative complement pathway in the two survivors and in one healthy boy belonging to the family was reduced, as measured in a kinetic system. These three individuals had 10-11% of normal properdin concentration in plasma, as measured by a catching ELISA method, while the other complement components were normal. Hemolytic complement activity was normalized when purified properdin was added. The data are compatible with an X-linked mode of inheritance of properdin deficiency.