A deletion of the DJ-1 gene in a Dutch family and a mutation conferring a functionally inactive form in an Italian family associated with early onset PD were first observed in 2001 [50], and confirmed in 2003 [51] (as is convention, we use italics to indicate the gene and non-italics to indicate the protein; thus, DJ-1 means the gene, and DJ-1 means the protein). Here, PARK7 is linked to Parkinson disease.