Hereditary properdin deficiency in three families of Tunisian Jews.

Hereditary properdin deficiency is a rare genetic disorder of the complement system. Three propositi and six additional family members with properdin deficiency have been found following analysis of the hemolytic activity of the classical (CH50) and the alternative (AP50) complement pathways in the sera of 101 survivors of meningococcal infections and 59 survivors of severe pneumococcal and Haemophilus influenza infections. All the properdin-deficient individuals had undetectable levels of properdin by radial immunodiffusion and by Western blotting. They belonged to three non-related families of Tunisian Jews who came from different parts of Tunisia. Two patients had a meningococcal infection at 15 and 16 years of age, respectively, and one had Haemophilus influenza meningitis at 1.5 years of age. In contrast to the fulminant and fatal course of meningococcal infection which was previously described in some properdin-deficient patients, our patients had a relatively mild disease. Properdin deficiency may not be as rare as previously thought. Analysis of AP50, in addition to CH50, in sera of patients who had meningococcal infection, will probably disclose many more cases of hereditary properdin deficiency. In addition, our findings indicate that, as in other complement abnormalities, hereditary properdin deficiency may also be associated with the ethnic origin of the patient.