The objective of this study was to establish whether known pathogenic mutations (LRRK2 c.6055G > A, LRRK2 c.4321C > G and SNCA c.209G > A) are present in Maltese PD and PS cases, and to determine whether the functional MTHFR c.677C > T and c.1298A > C, QDPR c.68G > A and SPR c.596-2A > G genetic variants alter susceptibility to PD. The gene discussed is MTHFR; the disease is Parkinson disease.