Dr. Charlotte Sumner describes how SMA is inherited
What is SMA?
Spinal Muscular Atrophy (SMA) is an inherited disease that affects approximately 1 in 10,000 infants born in the U.S. each year. There are four types of SMA, based on the degree of symptoms, with SMA Type I being the most severe.
Cause and Inheritance
SMA is caused by an alteration in the SMN1 gene, which results in reduced levels of a protein called Survival Motor Neuron (SMN). The SMN protein is critical to the survival of nerve cells in the spinal cord responsible for muscle contraction. When these protein levels are reduced, the muscles do not function properly and become smaller and weaker (“atrophy”). SMA is an autosomal recessive disease, meaning that a person must have two copies of an altered SMN1 gene to have the disease.
Dr. De Vivo provides an overview of SMA and describes the four SMA types
Dr. Sumner explains the cause of SMA and the two genes, SMN1 and SMN2
Frank, an SMA parent, describes the genetics of SMA
Children with SMA generally appear normal at birth, with symptoms developing as early as a few months after birth. A diagnosis of SMA is usually confirmed by a genetic test to identify a mutation in the SMN1 gene.
Dr. De Vivo discusses the diagnosis of SMA
James talks of having a child with very severe Type I SMA
Esther and Frank talk about the diagnosis of their daughter, Maeve