To date, more than 80 genes or sites have been identified, of which SPAST (previously known as SPG4; OMIM:604277) and SPG11 (OMIM:610844) appear to be the most common genetic cause of the AD‐HSP and AR‐HSP, respectively (Boutry et al., 2019; Klebe et al., 2015). The gene discussed is SPAST; the disease is Alzheimer disease.