SMPD1 and Parkinson disease: In summary, our stratified analysis suggests that intermediate- size hexanucleotide repeats in C9orf72 are a risk factor for PD in individuals who do not carry common AJ founder mutations in LRRK2, GBA, or SMPD1. These results should be interpreted with caution as no correction for multiple comparisons was performed, and similar analyses should be performed on a larger cohort of PD patients.