Hypomyelination with atrophy of basal ganglia and cerebellum

Alternate names

H-ABC; Leukodystrophy, hypomyelinating, 6; HLD6; Leukodystrophy, hypomyelinating, with atrophy of the basal ganglia and cerebellum; HABC

Definition

Hypomyelination with atrophy of basal ganglia and cerebellum (H-ABC) is a disease that affects certain parts of the brain.

Epidemiology

H-ABC is very rare. While the exact prevalence is unknown, as of 2016, 71 people with H-ABC have been reported.

Cause

• Hypomyelination with atrophy of basal ganglia and cerebellum (H-ABC) is caused by a mutation in the TUBB4A gene.
• The mutation typically occurs for the first time in a person with the condition (i.e. it typically is not inherited from a parent).
• The TUBB4A gene is involved in the formation of microtubules.
• Microtubules are an important part of the cytoskeleton (which gives cells their shape).
• They also play important roles in many cellular processes such as cell division, motility, and transport.
• The TUBB4A gene is mostly expressed ("turned on") in the central nervous system (CNS), especially in parts of the brain affected by H-ABC.

Gene mutations

• Mutations in this gene are thought to impair the formation or stability of microtubules.
• This in turn may impairs the structure or roles of cells in the CNS, leading to the signs and symptoms of H-ABC.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

Inheritance is autosomal dominant, but most cases are due to a new mutation occurring for the first time in a person with the condition.

Signs and symptoms

• Symptoms usually begin in infancy or early childhood and worsen over time.
• Severity of symptoms and rate of progression can vary.
• Symptoms may include delayed motor development, learning difficulties, upper-motor neuron dysfunction (spasticity, exaggerated reflexes, and Babinski signs), dystonia, rigidity, involuntary movements, and speech and swallowing problems.

Diagnosis

• H-ABC is diagnosed based on the presence of characteristic symptoms, a magnetic resonance imaging (MRI) scan of the brain, and genetic testing confirming a mutation in the TUBB4A gene.

Treatment

Unfortunately, there is currently no cure for hypomyelination with atrophy of basal ganglia and cerebellum (H-ABC).

However, quality of life may be improved with management of individual symptoms of the condition, which may involve:

• Medications and physical therapy for spasticity (e.g. baclofen, diazepam or intramuscular botulinum toxin)
• Medications for dystonia (e.g. trihexyphenidyl, tetrabenazine, or high doses of levodopa and carbidopa which were reportedly helpful in case reports)
• Gastrostomy for feeding for swallowing dysfunction
• Routine treatment for seizures, constipation, and gastroesophageal reflux disease
• Routine evaluations of swallowing and feeding, nutrition, orthopedic and joint integrity, and neurologic symptoms are recommended.

NIH genetic and rare disease info

• NIH info on Hypomyelination with atrophy of basal ganglia and cerebellum

Hypomyelination with atrophy of basal ganglia and cerebellum is a rare disease.

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