Between 1998 and 2004, studies of families, often consanguineous, affected by early-onset forms of PD with a suspected autosomal recessive inheritance pattern identified biallelic loss of function variants in PRKN (previously called Parkin) [51], PARK7 (previously called DJ-1) [52] and PINK-1 [53]. Here, PINK1 is linked to Parkinson disease.