However, the proposition of SLC33A1S113R as the causative mutation was challenged by the reports that no SLC33A1 mutation has been detected in other HSP cases and homozygous mutations in SLC33A1 cause a lethal recessive disorder with the phenotypes of congenital cataracts, hearing loss, and low serum copper and ceruloplasmin (Schlipf et al., 2010; Huppke et al., 2012). The gene discussed is SLC33A1; the disease is hereditary spastic paraplegia.