Inclusion Criteria:  For all patients:  Person who was informed of the study and who did not object to inclusion Age ≥ 18 years Patient affiliated to national health insurance Onset of symptoms strictly more than 2 years and less than 7 years ago Inclusion in the "NS-park" national database Patient with a recent brain MRI to exclude patients with secondary parkinsonism (vascular parkinson,hydrocephalus at normal pressure)  For patients in the "idiopathic Parkinson's disease group" :  - Idiopathic Parkinson's disease that is "possible," "probable," or "definite" according to UKPDSBB (UK Parkinson's Disease Society Brain Bank, Hughes et al. 1992) criteria.  For patients in the "atypical parkinsonian syndrome" group:  Subjects with a "possible" or "probable" diagnosis of MSA according to the diagnostic criteria of Gilman et al, 2008 Or Subjects with a "possible" or "probable" diagnosis of AP according to the diagnostic criteria of Hoglinger et al, 2017 Or Subjects with a "possible" or "probable" diagnosis of CBD according to the diagnostic criteria of Armstrong et al, 2013  Exclusion Criteria:  For all patients:  Disability making it impossible for him/her to participate in the trial due to lack of understanding of the information provided to him/her Patient under guardianship, curatorship or a measure of judicial protection Patients with any other neurological disease that could bias the results of our study: stroke, brain tumor, other neurodegenerative disease of the nervous system. Patients with secondary Parkinsonism (iatrogenic, toxic, inflammatory, post-traumatic) Patients with dyslipidemia receiving lipid-lowering treatment (statins, fibrates, inhibitors of intestinal cholesterol absorption). Patients with a progressive systemic disease that affects cholesterol metabolism, peroxisomal or mitochondrial function. (Examples: familial hypercholesterolemia, mitochondriopathy, peroxisome biogenesis disorders, etc.) Patient with a chronic disability making it impossible to collect clinical and cognitive data. Pregnant or breastfeeding women