Compound heterozygosity of a novel missense variant and exonic deletion in hypomyelinating leukodystrophy 15.

Hypomyelinating leukodystrophy 15 (HLD15) results from biallelic pathogenic variants in EPRS1, but exonic deletions have not been reported. We describe a 40-year-old woman with mild intellectual disability, ataxia, dystonia, and MRI showing hypomyelination. Whole-exome sequencing identified a heterozygous missense variant in the prolyl-tRNA synthetase domain of EPRS1 (c.3430 C > G; p.Leu1144Val, NM_004446.3), without second variant. Whole-genome sequencing revealed a heterozygous 220-bp deletion spanning exon 15 (c.1743-30_1932del), and segregation analysis confirmed compound heterozygosity. RT-PCR from lymphoblastoid cells demonstrated exon-15 skipping leading to a frameshift (p.Asn582Serfs*10) and nonsense-mediated decay, leaving predominant expression of the paternally inherited missense allele. These findings support loss-of-function for the deletion and classify c.3430 C > G as likely pathogenic under ACMG/AMP criteria (PM1, PM2, PM3, PP3). This case represents the first exonic deletion reported in EPRS1. The relatively mild, adult-onset phenotype broadens both mutational and clinical spectra of HLD15 and highlights the importance of structural-variant analysis when only a single candidate variant is detected in recessive leukodystrophy.