It will be important to determine whether this is also the case for other HSP subtypes with lysosomal abnormalities, including the subtypes caused by mutations in AP-5, SPG11, and SPG15 as well as the subtype caused by mutations in the SPG8 gene, which encodes a retromer-associated protein, strumpellin [49]. This evidence concerns the gene SPG11 and hereditary spastic paraplegia.