Partial lipodystrophy and familial C3 deficiency.

A familial deficiency of C3 in the family of a patient with partial lipodystrophy is reported for the first time. This genetic defect is termed hypomorphism of C3 fast (C3f). The defect is detected by analysis of C3 phenotype by densitometry and crossed gel-immunoelectrophoresis; all affected individuals have had reduced serum C3 (lower than 2 SD below mean) on at least one occasion. The possibility that partial lipodystrophy and the frequently associated glomerulonephritis occur in immunologically deficient individuals is supported by this observation.