Interestingly, while both brothers did not present alterations in the main PD-related genes (i.e., PRKN, PINK1, and DJ-1), a homozygous missense mutation (c.835G > A) in the adenosine A1 receptor (A1R) gene (ADORA1) was found (Jaberi et al., 2016). Here, PRKN is linked to Parkinson disease.