Should ITSN1 be considered as a Mendelian Parkinson's disease gene? Description of three novel families

Rare loss-of-function variants in ITSN1 were recently reported to confer a high risk for Parkinson's disease (PD). From our local large exome sequencing dataset of PD cases, we identified five carriers from three families. Clinical features of ITSN1-PD are typical and responsive to standard treatments. Additionally, we discuss whether ITSN1 loss-of-function variants should only be considered as a high-risk factor or a Mendelian PD gene.