What is Spinal Muscular Atrophy?
SMA is a deadly and relatively common genetic disease and is the leading genetic cause of death in infants and toddlers. It is the absence/defect in the Survival Motor Neuron Gene (SMN1) that causes Spinal Muscular Atrophy. The SMN1 gene codes for survival of motor neuron (SMN) protein, and this protein is critical to the survival and health of motor neurons, nerve cells in our spinal cord that our brain uses to control our muscles. Without sufficient SMN protein, motor neurons shrink and die. As the motor neuron network breaks down, the ability of the brain to control muscles diminishes and with less control and use, muscles weaken and waste away.
The name Spinal Muscular Atrophy (SMA) refers to several related neuromuscular diseases that all have the same basic cause, although they differ considerably in age of onset and severity. SMA occurs in approximately 1/10,000 births, and SMA Type I, which is the most severe form of this disease, is the most common single genetic cause of death in infancy. There is currently no cure for SMA or treatment to stop its progression. Medical care and physical therapy may help prevent complications and ensure the best possible quality of life for those affected. The shared feature of all the forms of SMA is progressive muscle weakness and wasting caused by degeneration of the anterior horn cells of the spinal cord (also called the lower motor neurons). Normally these nerve cells relay messages from the brain to the muscles and stimulate them to contract. Without this stimulation, the muscles atrophy. Eventually, in addition to generalized muscle weakness and wasting, particularly in the trunk,
Spinal muscular atrophy is a group of inherited disorders that cause progressive muscle degeneration and weakness. Spinal muscular atrophy (SMA) is the second leading cause of neuromuscular disease. It is usually inherited as an autosomal recessive trait (a person must get the defective gene from both parents to be affected). There are several types of SMA called subtypes. Each of the subtypes is based on the severity of the disorder and the age at which symptoms begin. There are three types of SMA that affect children before the age of 1 year. There are two types of SMA, type IV and Finkel type, that occur in adulthood, usually after age 30. Symptoms of adult-onset spinal muscular atrophy are usually mild to moderate and include muscle weakness, tremor and twitching. The prognosis for individuals with SMA varies depending on the type of SMA and the degree of respiratory function. The patient’s condition tends to deteriorate over time, depending on the severity of the symptoms. Spinal
Spinal Muscular Atrophy (SMA) Types I, II, and III belong to a group of hereditary diseases that cause weakness and wasting of the voluntary muscles in the arms and legs of infants and children. The disorders are caused by an abnormal or missing gene known as the survival motor neuron gene (SMN1), which is responsible for the production of a protein essential to motor neurons. Without this protein, lower motor neurons in the spinal cord degenerate and die. The type of SMA (I, II, or III) is determined by the age of onset and the severity of symptoms. Type I (also known as Werdnig-Hoffman disease, or infantile-onset SMA) is evident at birth or within the first few months. Symptoms include floppy limbs and trunk, feeble movements of the arms and legs, swallowing difficulties, a weak sucking reflex, and impaired breathing. Type II (also known as juvenile SMA, intermediate SMA, or chronic SMA, has an onset between 6 and 18 months. Legs tend to be more impaired than arms. Children with Type
