Molecular genetic analysis of the P-450C18 gene is three patients from three different families affected with CMO II deficiency has indicated that a point mutation of CGG----TGG (181Arg----Trp) in exon 3 and one of GTG----GCG (386Val----Ala) in exon 7 occur exclusively in the gene of the patients.
All individuals affected with CMO-II deficiency were homozygous for both mutations, whereas eight asymptomatic subjects were homozygous for R181W alone and three were homozygous for V386A alone.