Spinal Muscular Atrophy (SMA)
Spinal Muscular Atrophy (SMA) refers to a group of diseases which affect the motor neurons of the spinal cord and the brain stem. These are very important cells that are responsible for sending signals to the muscle cells. Without proper input from the motor neuron, the muscle cells will become much smaller (atrophy) and will produce symptoms of muscle weakness. Degeneration and death of the motor neurons in the key organs such as brain and spinal cord leads to weakness in the muscles connected with swallowing, breathing and walking. The incidence of SMA is between 1 in 6000 to 1 in 10,000 live births with a carrier frequency of 1 in 50 all over the world. There are 4 types of SMA which can be categorized according to the age of onset, mode of inheritance, distribution of muscle weakness and progression of symptoms. The most common cause of SMA is due to deficiency of a motor neuron protein called SMN (Survival Motor Neuron).