Genetic studies of the frequencies of mutant alleles for coding cytochrome P-450 monooxygenase (CYP 2D6) in Parkinson's disease (PD) patients have been inconsistent.
However, other hypotheses have been suggested: impairment of neuronal CYP 2D6 expression, transient modification of CYP 2D6 phenotype, or linkage of CYP2D6 gene to the candidate gene locus directly involved in IPD.