SNP Shot: Genomic Insights

Hypomyelination with brainstem and spinal cord involvement and leg spasticity (HBSL) is a disorder impacting the central nervous system, specifically the brain and spinal cord. It primarily affects nerve pathways, known as tracts, within the spinal cord and brainstem (the connection between the brain and spinal cord). HBSL falls under the category of leukodystrophies, a group of diseases characterized by white matter abnormalities in the nervous system. White matter is composed of myelin-coated nerve fibers, where myelin acts as insulation, ensuring swift nerve impulse transmission. In HBSL, the body's ability to produce myelin is impaired (hypomyelination).

Individuals with HBSL may initially develop motor skills (like rolling and sitting) normally, but movement difficulties generally emerge during their first year of life. However, onset can be delayed until adolescence in some cases. A hallmark of HBSL is spasticity (muscle stiffness) in the legs, which progresses over time. Consequently, most individuals with HBSL lose the ability to walk without assistance. Additional neurological issues may include involuntary eye movements (nystagmus), reduced muscle tone (hypotonia) in the trunk, and mild intellectual impairment.

Magnetic resonance imaging (MRI) scans reveal specific and identifiable brain changes in HBSL patients. These characteristic abnormalities are often observed in particular nerve tracts within the brainstem and spinal cord, notably the pyramidal tract, lateral corticospinal tract, and dorsal column.

Inheritance:

HBSL follows an autosomal recessive inheritance pattern. This signifies that both copies of the responsible gene in each cell must carry mutations for the condition to manifest. The parents of an affected individual each carry a single copy of the mutated gene, but they typically do not exhibit symptoms of the disorder.