Hypomyelination with Brainstem and Spinal Cord Involvement and Leg Spasticity (HBSL)
What is HBSL?
Hypomyelination with brainstem and spinal cord involvement and leg spasticity (HBSL) is a form of leukodystrophy that affects the brain and spinal cord, specifically the tracts that connect the two. In those affected by HBSL, the nervous system cannot produce a sufficient amount of myelin, which is the protective covering of nerve cells.
What are the symptoms of HBSL?
Symptoms typically begin with the first years of infancy. Affected individuals experience progressive stiffness in the legs that makes them unable to walk independently, along with abnormal eye movements, mild intellectual disability, and muscle weakness in the torso. Additional symptoms include:
- Lack of muscle coordination
- Difficulty talking
- Mental functioning deterioration
- Overactive reflexes
What causes HBSL?
The DARS1 gene is mutated in this condition, resulting in a decreased production of the aspartyl-tRNA synthetase enzyme. This enzyme is important in protein synthesis, but medical professionals are unsure as to how this mutation leads to the characteristic symptoms. They do know that it is passed down in an autosomal recessive pattern.
How is HBSL diagnosed?
MRIs are often used to see any brain abnormalities, and genetic testing is used to confirm a diagnosis.
What are the treatments for HBSL?
There is no cure for this condition; treatment is symptomatic and supportive.