The genetics of autosomal recessive early-onset Parkinson's disease.

Early-onset Parkinson's disease (EOPD) is usually defined as Parkinson's disease (PD) occurring before the age of 40-50 years. Unlike late-onset PD, EOPD is often due to pathogenic mutations in autosomal recessive genes. Two phenotypes can be distinguished: typical EOPD, which progresses slowly (PRKN, PINK1 and DJ-1), and atypical PD, often associated with additional symptoms (ATP13A2, FBXO7, DNAJC6, VPS13C, SYNJ1, PLA2G6). In this review, we will highlight recent advances and remaining challenges. The frequency of causal genetic mutations and the genotype-phenotype landscape of PRKN-associated PD has been refined. Long-read sequencing has solved several undiagnosed cases with a single PRKN mutation. Five new genes have been reported to contribute to EOPD associated with various neurological signs (PTPA, DAGLB, PSMF1, EPG5, SGIP1). Small molecules targeting PRKN dysfunctions are expected to enter clinical trials in the coming years, paving the way for targeted therapies in EOPD.