This type of SMA is much less common than types one to three. Symptoms usually include mild muscle weakness, tremor and twitching. SMA type 4 is also known as adult onset spinal muscular atrophy. SMA (all types) is a relatively common ‘rare disorder’ approximately 1 in 6000 babies born are affected, and about 1 in 40 people are genetic carriers. Spinal muscular atrophy (SMA) most often affects babies and children and makes it hard for them to use their muscles. When your child has SMA, there's a breakdown of the nerve cells in the brain and spinal cord. The brain stops sending messages that control muscle movement. When that happens, Author: Mary Jo Dilonardo.
Spinal Muscular Atrophy Type IV (Adult Onset) In the adult form, symptoms typically begin after age 35. It is rare for Spinal Muscular Atrophy to begin between the ages of 18 and 30. Adult onset SMA is much less common than the other forms. Spinal muscular atrophy (SMA) is characterized by muscle weakness and atrophy resulting from progressive degeneration and loss of the anterior horn cells in the spinal cord (i.e., lower motor neurons) and the brain stem nuclei. The onset of weakness ranges from before birth to adolescence or young adulthood.
A number sign (#) is used with this entry because autosomal recessive adult-onset spinal muscular atrophy type IV (SMA4) is caused by mutation or deletion in the SMN1 gene on chromosome 5q13. Allelic disorders with overlapping phenotypes of differing severity and age at onset include SMA type I (253300), SMA type II (253550), and SMA type III (253400). Spinal muscular atrophy is a group of neuromuscular disorders that result in the loss of motor neurons and progressive muscle wasting. The severity of symptoms and age of onset varies by the type. Some types are apparent at or before birth while others are not apparent until adulthood. All generally result in worsening muscle weakness associated with muscle twitching. Arm, leg and respiratory muscles Complications: Scoliosis, joint contractures, pneumonia.
Adult Spinal Muscular Atrophy is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health (NIH). This means that Adult Spinal Muscular Atrophy, or a subtype of Adult Spinal Muscular Atrophy, affects less than 200,000 people in the US population. Spinal Muscular Atrophy UK has more information about type 3 SMA. Type 4 SMA (adults) Type 4 SMA, also called adult-onset SMA, usually begins in early adulthood. Someone with the condition may have: weakness in the hands and feet ; difficulty walking shaking and twitching muscles ; Type 4 SMA gets slowly worse over time, but doesn't normally cause problems with breathing or swallowing.