SMA is divided into subtypes based on age of onset and maximum function achieved. SMA types 0, 1, 2, 3 and 4 are inherited as autosomal recessive genetic disorders and are associated with mutations in the SMN1 gene, which is located on chromosome 5.1
Spinal Muscular Atrophy Type 1
SMA type 1, also called Werdnig-Hoffman disease, is another severe form of SMA. It is the most common type of spinal muscular atrophy.1
Symptoms of SMA type 1 may be present at birth or within the first few months of life. These infants usually have difficulty breathing and swallowing, a weak sucking reflex,2 floppy limbs and trunk, feeble arm and leg movements (poor muscle tone), and impaired breathing. The legs tend to be more impaired than the arms,3 and a twitching of the tongue is often seen. While the body is significantly affected by Spinal Muscular Atrophy type 1, intelligence in these children is normal.1
Children with SMA type 1 likely will only be able sit upright with support.
The rate of progression of SMA type 1 varies. Within a few months, breathing and bowel (constipation) difficulties may develop. Respiratory failure may occur or food inhaled onto the lungs may cause choking.
These children usually survive up to age 2 without respiratory assistance. They can survive longer, however, if given respiratory support.
Follow the latest developments for all experimental Spinal Muscular Atrophy treatments on the SMA Therapy Tracker.
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