ENTPD1 and Autosomal recessive spastic paraplegia type 64: After NGS sequencing and cosegregation analysis, the variant c.401T>G (p.M134R) in the ENTPD1 gene, for which both sisters were homozygous, was identified as a mutation responsible for a complicated form of HSP, autosomal-recessive spastic paraplegia type 64 (SPG64).