Genetically determined low C4: a predisposing factor to autoimmune chronic active hepatitis.
Of 26 patients with autoimmune chronic active hepatitis (CAH) starting in childhood 18 (69%) had low C4 and 5 (19%) had low C3 serum levels. Impaired hepatic synthesis and immune-consumption were unlikely since transferrin levels were normal in all patients, albumin levels were persistently low in only 3, and only 3 had raised levels of activation fragment C3d. C4d was normal in all patients studied. In the families of 12 probands with low C4, 7 parents had low C4 and 2 had levels which were at the lower limit of normal. 5 of 10 siblings from 5 families had low C4. These results suggest that low C4 levels in CAH are genetically determined. C4 phenotyping in 20 patients and in 26 parents showed that 90% and 81%, respectively, had null allotypes at either the C4A or C4B locus compared with 59% in controls, indicating that defective expression of structural genes may contribute to the observed C4 deficiency.
Vergani
D
D
Wells
L
L
Larcher
V F
VF
Nasaruddin
B A
BA
Davies
E T
ET
Mieli-Vergani
G
G
Mowat
A P
AP
D000293:Adolescent; D000328:Adult; D001327:Autoimmune Diseases / Q000097:blood / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D003176:Complement C3 / Q000172:deficiency / Q000235:genetics; D003181:Complement C4 / Q000172:deficiency / Q000235:genetics*; D004198:Disease Susceptibility; D005260:Female; D005796:Genes; D006521:Hepatitis, Chronic / Q000097:blood / Q000235:genetics* / Q000276:immunology; D006801:Humans; D008297:Male; D010641:Phenotype; D011110:Polymorphism, Genetic
D003176:Complement C3; D003181:Complement C4