Additive congenital anomaly patterns.

A family study was conducted on 1,038 index patients with unidentified multiple congenital abnormality (MCA) patterns in the population-based material of the Hungarian Congenital Malformation Registry (HCMR). Congenital abnormalities (CAs) were detected in 5.1% of fathers and in 4.2% of mothers, respectively. Two fathers had an MCA pattern similar to that in their affected child. One component CA of multimalformed index children occurred in 55.1% of fathers and 52.3% of mothers. Thus, in more than half of affected parent-child pairs, there may be a causal connection between the observed anomalies. The combination of CAs of different parental origin in index patients is called "additive CA pattern." This group of patients may represent about 5% of unidentified MCA patterns and about 50% of affected parent-child pairs.