SIMULTANEOUS OCCURRENCE OF HEREDITARY C6-DEFICIENCY AND C2-DEFICIENCY IN A FRENCH-CANADIAN FAMILY

Abstract

The sera of 4 sisters were found to lack the 6th component of complement (C6) and the serum of one was also partially deficient in C2. Two other blood relatives were heterozygous for both deficiencies; only 1 sibling had normal values. The father of these 8 siblings was heterozygous for C2D and C6D and in the 3rd generation, 6 children were heterozygous for C6 deficiency. The C6 deficiency was not linked to the HLA system, but the C2 deficiency segregated with the haplotype A10,B18. The proband, homozygous for C6 deficiency, was treated for chronic active brucellosis and in another sibling with C6 deficiency, toxoplasmosis was diagnosed. Neither bleeding disorders nor a tendency to collagen diseases were observed and the opsonic activity was normal in the sera of all family members.