Spinal Muscular Atrophy
Overview
Plain-Language Overview
Spinal Muscular Atrophy is a genetic disorder that affects the nervous system, specifically the nerve cells that control muscle movement. It causes progressive muscle weakness and loss of motor function, primarily in the arms and legs. This condition results from the loss of specialized nerve cells called motor neurons in the spinal cord. As these neurons die, muscles become weaker and may eventually waste away. The severity of symptoms can vary widely, but it often leads to difficulties with activities like walking, swallowing, and breathing. Early diagnosis is important to understand the progression and manage symptoms effectively.
Clinical Definition
Spinal Muscular Atrophy is a hereditary neuromuscular disorder characterized by degeneration of anterior horn cells in the spinal cord, leading to progressive muscle atrophy and weakness. It is most commonly caused by homozygous deletions or mutations in the SMN1 gene, which encodes the survival motor neuron (SMN) protein essential for motor neuron maintenance. The disease manifests with varying severity, classified into types based on age of onset and motor milestones achieved. The loss of motor neurons results in impaired voluntary muscle movement, predominantly affecting proximal muscles. Respiratory failure is a major cause of morbidity and mortality. Diagnosis is confirmed by genetic testing identifying biallelic SMN1 mutations. The condition is a leading genetic cause of infant mortality.