Comprehensive Guide to Understanding Spinal Muscular Atrophy

Comprehensive Overview of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a genetic disorder that impacts the nerves responsible for controlling voluntary muscle movements. The nerve cells affected are primarily located in the spinal cord, which explains the term "spinal" in the disease name. The term "muscular" refers to the disease's effect on muscles, which weaken due to lack of neural signals. SMA involves the degeneration of motor neurons within the spinal cord, classifying it as a motor neuron disease affecting muscle strength and function.

Causes of Spinal Muscular Atrophy

SMA is a hereditary condition present from birth.

Children with SMA inherit two copies of a defective gene from their parents.

This genetic mutation prevents the production of a vital protein called SMN (Survival of Motor Neuron), crucial for motor neuron health.

Carriers have only one defective gene and typically show no symptoms but can pass the gene to their offspring.

Signs and Symptoms of Spinal Muscular Atrophy

Symptoms vary depending on the SMA type:

Type 1, the most severe form, causes profound muscle weakness, inability to support the head or sit, and often leads to respiratory issues. Infants with this form rarely survive beyond two years.

Type 2, often called chronic infantile SMA, affects children between 6-18 months. It primarily impacts leg muscles, with affected children able to sit or stand with support.

Type 3, known as juvenile SMA, affects children aged 2 to 17. These children can walk, sit, and stand unaided but may struggle with running or climbing and might require a wheelchair later.

Type 4 is adult-onset SMA. Symptoms include muscle twitching, weakness, and breathing difficulties.