An atypical case of SPG56/CYP2U1-related spastic paraplegia presenting with delayed myelination.

Hereditary spastic paraplegia (HSP) is a neurological disorder characterized by a progressive spasticity and muscle weakness of the lower limbs. It is divided into two subtypes, uncomplicated and complicated forms. Biallelic mutations in the cytochrome P450 2U1 gene (CYP2U1) are associated with spastic paraplegia type 56 (SPG56), manifesting both uncomplicated and complicated HSP. Accompanying clinical features include intellectual disability, dystonia, cerebellar ataxia, subclinical peripheral neuropathy, visual impairment, as well as abnormalities in brain magnetic resonance imaging. As a rare clinical feature, delayed myelination has previously been reported in only two patients with CYP2U1 mutations. Here, we report a patient with SPG56 with novel compound heterozygous mutations in CYP2U1 which were identified by whole exome sequencing. Our patient exhibited complex features together with delayed myelination, broadening the phenotypic spectrum of SPG56, and implying that CYP2U1 should be screened in HSP with delayed myelination.