Genetic polymorphism of factor B (Bf) and C3 component of complement in type 1 (insulin-dependent) diabetes mellitus: BFQO allele observed in a diabetic child.

: C3 and Bf polymorphisms were studied in 215 and 192 children with type 1 diabetes mellitus (IDDM), respectively. No significant differences in C3 phenotypes and allele frequencies were found between IDDM patients and a healthy population. The rare allele BfF1 was found in 9.37% of diabetic patients but in only 0.35% of the general Slovak population (0.0468 vs. 0.0017). An increased frequency rate of BfSO.7 was also observed in 8.85% of IDDM patients compared with 3.57% of healthy controls (0.0442 vs. 0.0178). The relative risk was 28.83 for BfF1 and 2.55 for BfSO.7. One diabetic child was found to be heterozygous for a silent allele BfQO. This rare Bf allele was transmitted to the boy from his healthy mother.