In 1998, an autosomal recessive form of HSP was associated with mutations in a gene (SPG7) encoding a protein (paraplegin) with strong similarities to the two homologous subunits of the yeast m-AAA protease [called Afg3 (Yta10) and Rca1 (Yta12)] (Casari et al., 1998). This evidence concerns the gene SPG7 and hereditary spastic paraplegia.