Alpha-synuclein Level in Saliva to Differentiate Between Idiopathic Parkinson Disease and Iatrogenic Parkinsonian Syndrome

Inclusion Criteria * The patient must have given their free and informed consent and signed the consent form * The patient must be insured or the beneficiary of an insurance policy * The patient is less than 55 years old * For patients with acquired parkinsonian syndrome (UKPDSBB criteria) currently at HOEHN and YAHR stage ≤3: * For patients recruited via a psychiatrist: after anti-dopamine treatment * For patients recruited via a neurologist: having a recent diagnosis (≤2 years) of Parkinson disease Exclusion Criteria: * The subject is participating in another study * The subject is in an exclusion period determined by a previous study * The patients is under judicial protection * The subject or their representative refused to sign the consent form * It proves impossible to give the subject or their representative clear information. * Patients with atypical degenerative parkinsonian syndrome * Patients with vascular, post-traumatic, metabolic, toxic or genetic parkinsonian syndrome * Appearance of parkinsonian syndrome prior to treatment with anti-dopamine * Injection of botulinum toxin into the salivary glands * Contra-indication on DAT-scan (unbalanced dysthyroidism, allergy, treatment with bupropion or amphetaminergics) * Poor oral health (polyposis, gingivostomatitis) observed during the odontologist visit * Patients not taking anti-psychotics with parkinsonian syndrome and normal DAT-scan