Hypomyelination with brainstem and spinal cord involvement and leg spasticity (HBSL), caused by aspartyl-tRNA synthetase (DARS1) gene mutations, is extremely rare, with only a few cases reported worldwide; thus, reports on HBSL treatment are few. The gene discussed is DARS1; the disease is hypomyelination with brain stem and spinal cord involvement and leg spasticity.