Types of Spinal Muscular Atrophies
The severity of spinal muscular atrophy can vary widely. As SMN1 genes are affected, the neuromuscular disorder is caused. As the fetus experiences breathing problems, the disorder symptoms begin to appear. SMA can cause mild muscle weakness in adults. Studies show that the classification of SMA into four types depends more on the motor mildest stone. As the smaller muscles of the body weaken, their size begins to decrease. SMA type 1 is the most severe of the different types of spinal muscular atrophy. It’s also known as SMA Type 0. SMA type 1, which is rare and fatal, causes severe symptoms. The most common forms of spinal muscular atrophy are listed below.
SMA Type 1 (Werding-Hoffmann disease)
SMA of this type is usually evident in infants before six months of age. Even during pregnancy, there is a decrease in movement. The babies are then born with breathing issues and spine contractures. The newborns can die in the first 12 months of life if they have SMN type 1. It is important to treat children with SMN Type 1. SMN type 1, among other symptoms, can cause tongue fasciculations (facial enlargement), swallowing problems, breathing difficulties, reduced limb movements and hypotonia. As they grow older, infants with SMA type 1, also develop curvature in the spine and other abnormalities of skeletal muscles. A child who does not seek treatment will never be able to sit or stand. Majority of SMA type I patients die before the age of 12. There are no treatments that can alter the disease, which increases life expectancy for SMA type 1. By using gene therapy, children with SMA type 1, can improve their motor skills such as walking and sitting.
SMA type 2, (The intermediate version)
Children with SMA type 2 start showing symptoms between 6-12 months. They are unable to stand or walk without assistance, but they can sit. Some children may lose their ability to sit independently for longer periods of time without seeking treatment. Some respiratory problems, such as hypoventilation can cause sleep issues. If no treatment is sought, the disease progresses differently in each patient with SMA type 2. The life expectancy of children with SMA type 2 is reduced, but they usually live until young adulthood. Children with SMA type 2 can improve their motor outcomes through proactive clinical care.
SMA Type 3 (Kugelberg-Welendr disease)
Children with SMA type 3 begin to show symptoms at 18 months of age. Children with SMA type 3 can walk independently but have difficulty walking, running, getting up from a seat, or climbing stairs. SMA type 3 is most prevalent in the proximal muscles located near the core of the body, closer to the legs. SMA type 3 sufferers are mainly affected by tremors that come and go in their hands. This is due to impaired signal transmission in the nervous systems. SMA type 3, if not treated, can also cause certain complications. SMA type three patients may experience complications such as chronic shortening or muscle around joints. Patients with SMA type 3 cannot freely move their joints, due to a reduction in muscle tone and strength. SMA patients with type 3 are more likely to experience respiratory problems later in life. Patients can live a normal lifespan if they receive proactive care. If the patient receives treatment to modify their disease, they can achieve developmental milestones such as fine and gross motor abilities.
SMA Type 4
Patients with SMA type 4 begin to develop symptoms after 21-years, displaying mild or moderate symptoms. The symptoms that are most prevalent in SMA type 4 include muscle weakness, muscle atrophy and proximal muscle weakening. SMA type 4, which usually affects adults, can be managed by using equipment or stretching to ease the symptoms.
Other Types of SMA
SMA can also be rarer and less common.
Distal Spinal Muscular Atrophy (DSMA),
This type of spinal muscle atrophy affects the lower legs, hands, feet, and arms.
Spinal Muscular Atrophy with Respiratory Distress (SMARD)
The SMARD can cause respiratory problems and even death in infants.
Kennedy disease or Spinobulbar Muscular Atrophy (SBMA).
SBMA is a rare form of spinal muscular atrophy that only affects men and begins in middle adulthood. This type of spinal muscle atrophy does not affect the life expectancy of patients.
