Genetic and Phenotypic Characterisation of Autosomal Recessive Parkinson's Disease in a Large Multicentre Cohort

Background: Genetic mutations causing autosomal recessive Parkinson's disease account for a significant proportion of patients with early-onset disease. However, no large multicentre studies of known recessive Parkinson's disease-linked genes have been performed, to guide genetic testing according to age at onset, family history, ethnic origin, or phenotype. We aimed to evaluate the relative frequencies of mutations in genes causing recessive Parkinson's disease and their associated phenotypes in a large series of European and North African cases. Methods: Clinical data for 1664 patients were collected between 1990 and 2018 from 511 families with recessive Parkinson's disease and/or with consanguinity, and 1098 isolated cases. All the recessively inherited genes were screened by Sanger and/or targeted next-generation sequencing and gene dosage methods. Clinical features were compared between patients with PRKN and those without mutations, by regression analyses adjusted for sex, age at onset, disease duration and levodopa medication. Findings: Biallelic mutations of genes known to cause recessive Parkinson's disease were found in 246 of the 1609 index cases (15·3%): 150 familial (29·4%) and 96 (8·7%) isolated cases. The most frequently mutated genes were PRKN, in 199 cases (12·4%), PINK1, in 23 (1·8%), and DJ-1, in two (0·16%). We screened 675 index cases by targeted sequencing, and 22 were found to have mutations in genes known to cause atypical parkinsonism (3·3%). PRKN and PINK1 mutation frequencies were higher in early-onset (≤40 years) than late-onset Parkinson's disease. The frequency of PRKN mutations in the 1609 index cases decreased with increasing age at onset, from 38% in cases ≤20 years to 4·4% in those with onset at 41 to 60 years. No mutation of PRKN or another recessive Parkinson's disease gene was found in patients with onset above 60. PRKN mutations were more frequent in Caucasians (13·4%) than in North Africans (7·4%). Conversely, PINK1 mutations were more frequent in North Africans (6·3%) than in Caucasians (0·9%). PRKN patients had an earlier age at onset, lower levels of asymmetry, akinesia, levodopa-induced motor complications, dysautonomia, and dementia than those without mutations. Interpretation: This is a large study providing information about the frequency of recessive Parkinson's disease genes according to age at onset, family history, ethnic origin, and associated phenotype. Its findings will be useful for genetic testing and counselling. Funding Statement: Fondation de France, France-Parkinson Association, la Federation pour la Recherche sur le Cerveau, the French program "Investissements d'avenir", National Institute for Health Research. Declaration of Interests: SL reports grants from Fondation de France, the French program “Investissements d’avenir” (ANR-10-IAIHU-06), both outside the scope of the submitted work. MA reports grants and personal fees from Abbvie, Teva, Aguettant, Actelion Pharmaceuticals, personal fees from Johnson and Johnson, Merz, Orkyn, all outside the scope of the submitted work. ER reports grants, personal fees and non-financial support from Orkyn, Aguettant, Merz pharma, Everpharma, personal fees and non-financial support from Movement Disorders Society, grants and non-financial support from Elivie, non-financial support from Merck, Dystonia Coalition, Dystonia Medical Research Foundation, grants from Ipsen, Fondation Desmarest, Fonds de dotation Brou de Lauriere, Agence Nationale de la Recherche, AMADYS, personal fees from Medday pharma, Retrophin, European Academy of Neurology, International Association of Parkinsonism and related Disorders, all outside the submitted work. CT received fees from ALLERGAN and from MERZ. J-CC reports grants from Sanofi, personal fees from EverPharma, Denali, BrainEver, Theranexus, Air Liquide, all outside the scope of this work. EB reports grants from Medtronic France, Abbvie, UCB, and Aguettant laboratories but no conflict of interest nor financial concerns about the present research paper submitted for publication. AB reports grants from ANR - Agence nationale de recherche, ARNN - Association pour la Recherche en Neuro-imagerie et Neuropsychologie, France Parkinson, AP-HP, FMR - Fondation Maladies Rares (ex GIS), France Parkinson + FRC (Federation pour la Recherche sur le Cerveau), Universite Mohammed V - Rabat, Prix Allianz Institut de France, RDS (Roger de Spoelberch Foundation), FDF -Fondation de France-, all outside the submitted work. All other authors have no competing interests to declare. Ethics Approval Statement: Informed consent was obtained from all participants, and genetic studies were approved by local ethics committees (INSERM, CCPPRB du Groupe Hospitalier Pitie-Salpetriere, Paris, France).