X-linked spinal muscular atrophy type 2

A rare genetic disorder affecting the spinal cord

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X-linked spinal muscular atrophy type 2 is a rare genetic disorder characterized by progressive muscle weakness and atrophy due to the degeneration of motor neurons in the spinal cord. This condition is inherited in an X-linked recessive pattern, primarily affecting males, while females are typically carriers.

Pathophysiology

X-linked spinal muscular atrophy type 2 is caused by mutations in the UBE1 gene, which is located on the X chromosome. The UBE1 gene encodes a protein involved in the ubiquitin-proteasome system, a critical pathway for protein degradation and turnover in cells. Mutations in this gene disrupt normal protein degradation, leading to the accumulation of damaged proteins and subsequent motor neuron degeneration.

Clinical Features

The clinical presentation of X-linked spinal muscular atrophy type 2 includes:

• Progressive muscle weakness, particularly in the proximal muscles of the limbs.
• Muscle atrophy, especially in the shoulder and pelvic girdle regions.
• Hypotonia, or decreased muscle tone.
• Delayed motor milestones, such as sitting and walking.
• Respiratory difficulties due to weakness of the respiratory muscles.

Diagnosis

Diagnosis of X-linked spinal muscular atrophy type 2 is based on clinical evaluation, family history, and genetic testing. Electromyography (EMG) and nerve conduction studies may be used to assess the extent of motor neuron involvement. Genetic testing can confirm the diagnosis by identifying mutations in the UBE1 gene.

Management

There is currently no cure for X-linked spinal muscular atrophy type 2. Management focuses on supportive care to improve quality of life and may include:

• Physical therapy to maintain muscle strength and flexibility.
• Occupational therapy to assist with daily activities.
• Respiratory support, such as non-invasive ventilation, for those with respiratory muscle weakness.
• Nutritional support to ensure adequate caloric intake and prevent malnutrition.

Prognosis

The prognosis for individuals with X-linked spinal muscular atrophy type 2 varies depending on the severity of the condition. Progressive muscle weakness can lead to significant disability, and respiratory complications are a common cause of morbidity.

Related pages

• Spinal muscular atrophy
• Motor neuron disease
• Genetic disorders
• X-linked recessive inheritance