PI4KA and hereditary spastic paraplegia: In the candidate list, we found novel disease genes already identified in our HSP/CA patient cohort, such as (i) SHMT2 (OMIM #619121), mutated in patient IDSPG26 [39] Fig. 5B; (ii) PI4KA (OMIM # 616531), mutated in patients IDSPG16 and IDSPG149 [38]; (iii) UBAP1, (OMIM #618418), mutated in patient IDSPG76 [41] Fig. 5C; (iv) PCYT2 (OMIM # 618770), mutated in patient IDSPG27 [40] Fig. 5D; and (v) DLG4 (OMIM # 18793), mutated in patient IDSPG107 [42].