Pathogenic variants in KIF1A have been linked to four clinical different disorders: (i) neuropathy, hereditary sensory, type IIC (HSNIIC, MIM # 614213); (ii) Spastic Paraplegia 30, autosomal recessive (SPG30, MIM # 610357); (iii) Spastic Paraplegia 30, autosomal dominant (SPG30, MIM # 610357); and iv) neurodegeneration and spasticity with or without cerebellar atrophy or cortical visual impairment (NESCAV syndrome, NESCAVS, MIM # 614255, formerly known as mental retardation autosomal dominant 9). The gene discussed is KIF1A; the disease is intellectual disability, autosomal dominant 9.