Molecular basis of hypokalemic myopathy caused by 17alpha-hydroxylase/17,20-lyase deficiency.

We describe a 28-year-old woman presenting with hypokalemic myopathy caused by 17alpha-hydroxylase/17,20-lyase deficiency caused by a homozygous mutation consisting of a G-to-C transition in the initiation codon in exon 1 of the CYP17 gene resulting in expression of an enzymatically inactive truncated P450c17 protein.