No abstract

The molecular basis of 5 alpha-reductase (5 alpha R) deficiency was investigated in four patients from three European families. In the French family, the first patient was raised as a female, and gonadectomy was performed before puberty. The second sibling, also raised as female, differed in that gonadal removal was performed after the onset of pubertal masculinization. The other two patients, both from Polish families, developed masculinization of external genitalia during puberty. All patients developed a female sexual identity. In all cases, no known consanguinity or family history of 5 alpha R deficiency was reported. The genomic DNAs of the patients were sequenced after polymerase chain reaction amplification of the five exons of the 5 alpha R type 2 gene. We found two homozygous mutations responsible for glutamine to arginine and histidine to arginine substitution in families 1 and 3, respectively. In family 2, we found a heterozygous mutation responsible for an asparagine to serine substitution at position 193. The glutamine/arginine 126 mutation in the French family was previously reported in a Creole ethnic group, and the Polish histidine/arginine 231 mutation was previously reported in a patient from Chicago. Moreover, all of the mutations created new restriction sites, which were used to determine the kindred carrier status in the three families. Because 5 alpha R deficiency is known to be a heterogenous disease in terms of clinical and biochemical expression, our data suggest that molecular biology analysis of the type 2 gene could be an essential step in diagnosing 5 alpha R deficiency.

This is the third deletion described in the 5 alpha-reductase type 2 gene. The deleted methionine 157 is conserved in both types 1 and 2 of human and rat 5 alpha-reductase, which suggests its crucial role in the functioning of the enzyme. This gene rearrangement was thus clearly responsible for the reduced 5 alpha-reductase activity and abnormal genital development in this patient.