In patients suffering from severe neurodegenerative disorders, homozygous recessive mutations in the KIF1A gene were first described as hereditary sensory and autonomic neuropathy type 2 and as three consanguineous families with an autosomal recessive form of hereditary spastic paraplegia (HSP) with an autosomal dominant form of SPG30 [16]. The gene discussed is KIF1A; the disease is hereditary spastic paraplegia.