Identification of the mutations in the parents of a patient with a putative compound heterozygosity for acute intermittent porphyria.

The molecular abnormalities responsible for acute intermittent porphyria were investigated in both parents of a girl who was retrospectively diagnosed as having a homozygous form of the disease. The mutations in the parents are different from each other and both of them correspond to previously identified G to A changes in the coding part of the porphobilinogen deaminase mRNA. These point mutations lead to the presence of a catalytically-defective but immunologically-reactive enzyme. Our results support the conclusion that the propositus girl may represent the first case of compound heterozygosity for acute intermittent porphyria alleles.