Mutations in PARK2, encoding Parkin, are the most frequent cause of juvenile PD (JPD), accounting for up to 50% of the cases with an age of onset <40 years (Kitada et al., 1998).PARK2 mutations range from single base pair substitutions, splice site mutations and small nucleotide deletions, to large deletions or duplications of one or more PARK2 exons; albeit through different mechanisms, all these variants probably have a “loss of function” effect. Here, PRKN is linked to juvenile Paget disease.