A rare genetic neurological disorder characterized by the association of hypomyelinating leukodystrophy with spondylometaphyseal dysplasia. Patients present in infancy with absent or delayed ability to walk independently, slowly progressive motor deterioration, spasticity, ataxia, proximal weakness, and joint contractures. Additional manifestations include mild cognitive impairment, short stature, scoliosis, enlarged and deformed joints, dysarthria, nystagmus, visual defects, and mildly dysmorphic features, among others. Mode of inheritance is X-linked recessive. The disease is spondyloepimetaphyseal dysplasia, Bieganski type (MONDO_0010275). Also known as: H-SMD, hypomyelination-spondyloepimetaphyseal dysplasia syndrome, leukoencephalopathy-SEMD syndrome, leukoencephalopathy-metaphyseal chondrodysplasia syndrome, spondyloepimetaphyseal dysplasia, X-linked, with hypomyelinating leukodystrophy, X-linked recessive.