SKP1 and Parkinson disease: Thus, the negative values of ALDH1A1PSMC4 and SKP1A suggest that these genes possibly decrease the risk for the occurrence of PD with OR values of 0.86, 0.73 and 0.73 respectively, whereas HSPA8 and HIP2 significantly increase the risk for PD, with OR values of 1.39 and 1.32, respectively.