Whereas some studies have found a reduction of α-syn levels in plasma via ELISA detection for the non-carriers and carriers of mutation LRRK2 [21], other studies have found similar α-syn levels [22], or higher α-syn levels in patients with PD [5] and other parkinsonian disorders such as Multiple System Atrophy compared to controls [23]. The gene discussed is LRRK2; the disease is Parkinson disease.