Hypomyelination with brainstem and spinal cord involvement and leg spasticity (HBSL)

DARS-related mutation


Autosomal recessive

Inheritance from both parents will result in the disease

Age range at onset:

Typically early infancy

Specialists you may see:


As well as spasticity in the legs, those with this condition commonly suffer from nystagmus, hypotonia and motor development delay. Some may develop seizures, dysarthria and learning difficulties.


Mutations in the DARS gene cause this condition. This leads to reduced activity of cytoplasmic aspartyl-tRNA synthetase, but it is not fully understood why this causes the specific symptoms of HBSL.

HBSL presents with similar symptoms to Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation, caused by mutations of the DARS2 gene, which relate to mitochondrial aspartyl- tRNA synthetase.