The deficiency of steroid 5 alpha-reductase leads to the disturbances in sex 
differentiation that cause symptoms of male pseudohermaphroditism. The methods 
of DNA analysis used to diagnose mutations of steroid 5 alpha-reductase gene 
(SRD5A2) were presented and discussed. Within the group of 21 patients with the 
deficiency of steroid 5 alpha-reductase 2 described so far in literature, the 
analysis of SRD5A2 gene revealed two "major" deletions, one "minor" deletion, 16 
point mutations (incl. 5 transitions and 11 transversions), in one case a 
mutation causing premature termination of translation and in one case mutation 
leading to defective splicing of the mRNA. The mutations localized in exons 2 
and 5 cause a decrease in affinity of 5 alpha-reductase 2 to the substrate 
(testosterone), while the mutations in exons 1 and 4, a decrease in affinity to 
the coenzyme (NADPH).