POLG and Parkinson disease: In 1997, the first PD-related gene was identified, and mutations are currently recognized in 23 genes (PARK1 to PARK23) that are directly related to PD as shown in Table 2 and Table 3 and in four genes (POLG, GBA1, TMEM230 and LRP10) whose alterations contribute to its development as shown in Table 4 [11].