[Analysis of CYP2U1 gene variants in a child with Hereditary spastic paraplegia type 56]

To analyze the clinical phenotype and genetic characteristics of a child with Hereditary spastic paraplegia (HSP).

A child with HSP who was admitted to the Third Affiliated Hospital of Zhengzhou University on August 10, 2020 due to discovery of tiptoeing for 2 years was selected as the study subject, and relevant clinical data was collected. Peripheral blood samples of the child and her parents were collected for the extraction of genomic DNA. And trio-whole exome sequencing (trio-WES) was carried out. Candidate variants were verified by Sanger sequencing. Bioinformatic software was used to analyze the conservation of variant sites.

The child was a 2-year-and-10-month-old female with clinical manifestations including increased muscle tone of lower limbs, pointed feet, and cognitive language delay. Trio-WES results showed that she had harbored compound heterozygous variants of c.865C>T (p.Gln289*) and c.1126G>A (p.Glu376Lys) of the CYP2U1 gene. And the corresponding amino acid for c.1126G>A (p.Glu376Lys) is highly conserved among various species. Based on guidelines from the American College of Medical Genetics and Genomics, the c.865C>T was predicted as a pathogenic variant (PVS1+PM2_Supporting), and c.1126G>A was rated as a variant of uncertain significance (PM2_Supporting+PM3+PP3).

The child was diagnosed with HSP type 56 due to compound variants of the CYP2U1 gene. Above findings have enriched the mutation spectrum of the CYP2U1 gene.