Combined homozygous factor H and heterozygous C2 deficiency in an Italian family.
Three of four children in a family have homozygous (less than 1% of normal) deficiency of factor H of the complement system and both parents, who are first cousins, are heterozygous for the same defect. The father and two of the H-deficient siblings also have a partial C2 deficiency. One of the children with combined deficiencies is affected by systemic lupus erythematosus with nephritis. No increased susceptibility to infections has been observed in the family. H deficiency is inherited in an autosomal codominant manner and is independently transmitted from C2 deficiency and HLA haplotypes. In the homozygous state it is associated with very low serum concentrations of B and C3, barely demonstrable as activated molecules. C5 is greatly reduced (less than 5%). Also, properdin and C6-9 are decreased. The findings in this family demonstrate that the occurrence of systemic lupus erythematosus in one of the children affected by a combined deficiency of factor H and C2 raises the question whether this pathology is related to the complete factor H or to the heterozygous C2 deficiency. Complete H deficiency is not necessarily accompanied by overt illness.
Brai
M
M
Institute of General Pathology, University of Palermo, Italy.
Misiano
G
G
Maringhini
S
S
Cutaja
I
I
Hauptmann
G
G
D002648:Child; D003175:Complement C2 / Q000172:deficiency* / Q000235:genetics; D003179:Complement C3b / Q000235:genetics; D003180:Complement C3b Inactivator Proteins / Q000172:deficiency* / Q000235:genetics; D011415:Complement Factor B / Q000235:genetics; D017242:Complement Factor H; D005260:Female; D008040:Genetic Linkage; D006680:HLA Antigens / Q000235:genetics; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007122:Immunoelectrophoresis; D008180:Lupus Erythematosus, Systemic / Q000235:genetics; D010375:Pedigree
C493495:CFH protein, human; D003175:Complement C2; D003180:Complement C3b Inactivator Proteins; D006680:HLA Antigens; D003179:Complement C3b; D017242:Complement Factor H; D011415:Complement Factor B