One example entails mutations in ER lipid raft-associated protein 2 (ERLIN2), which result in autosomal recessive pure as well as complex forms of HSP associated with cognitive decline (SPG18) (Alazami et al., 2011; Tian et al., 2016), and autosomal dominant pure HSP. The gene discussed is ERLIN2; the disease is hereditary spastic paraplegia.