About spinal muscular atrophy type iii

What is spinal muscular atrophy type iii?

Kugelberg Welander syndrome is a milder type of spinal muscular atrophy. It is a rare inherited neuromuscular disorder characterized by wasting and weakness in the muscles of the arms and legs, leading to walking difficulties in, and eventual loss of ambulation. Symptoms of Kugelberg Welander syndrome occur after 12 months of age. Patients learn to walk, may fall frequently and may have trouble walking up and down stairs at 2-3 years of age; some patients will not show functional changes until the teens. The legs are more severely affected than the arms. The long-term prognosis depends on the degree of motor function attained as a child.

Kugelberg Welander syndrome is inherited as an autosomal recessive trait. Molecular genetic testing has revealed that all types of autosomal recessive SMA (Werndnig-Hoffman disease, juvenile SMA and Kugelberg-Welander disease) are caused by mutations in the SMN (survival motor neuron) gene on chromosome 5. Deletion of the NAIP (neuronal apoptosis inhibitory protein) gene that is close to the SMN gene is also associated with SMA. More patients with Werdnig Hoffman disease (SMA1) than other types of SMA have NAIP deletions. The relationship between specific mutations in the SMN gene and nearby genes and the severity of SMA is still being investigated so classification of SMA subdivisions is based on age of onset of symptoms and maximum function achieved as opposed to the genetic profile.

What are the symptoms for spinal muscular atrophy type iii?

Breathing problemsbloo symptom was found in the spinal muscular atrophy type iii condition

Type 3. Symptoms for this type start when children are 2-17 years old. It's the mildest form of the disease. Your child will most likely be able to stand or walk without help but may have problems running, climbing stairs, or getting up from a chair. Later in life, they may need a wheelchair to get around.

Type 3 is also called Kugelberg-Welander disease or juvenile SMA.

What are the causes for spinal muscular atrophy type iii?

All four types of SMA result from a deficiency of a protein called SMN, which stands for “survival of motor neuron.” Motor neurons are nerve cells in the spinal cord that are responsible for sending out signals to our muscles.

When a mutation (mistake) occurs in both copies of the SMN1 gene (one on each of your two copies of chromosome 5), it leads to a deficiency in SMN protein. If little or no SMN protein is produced, it leads to motor function problems.

Genes that neighbor SMN1, called SMN2 genes, are similar in structure to SMN1 genes. They can sometimes help offset the SMN protein deficiency, but the number of SMN2 genes fluctuates from person to person. So the type of SMA depends on how many SMN2 genes a person has to help make up for their SMN1 gene mutation. If a person with chromosome 5–related SMA has more copies of the SMN2 gene, they can produce more working SMN protein. In return, their SMA will be milder with a later onset than someone who has fewer copies of the SMN2 gene.

What are the treatments for spinal muscular atrophy type iii?

The FDA has approved three medications to treat SMA: nusinersen (Spinraza), onasemnogene abeparvovec-xioi (Zolgensma) and risdiplam (Evrysdi). Both are forms of gene therapy that affect the genes involved in SMA. The SMN1 and SMN2 genes give your body instructions for making a protein that helps with controlling muscle movement.

  • Nusinersen (Spinraza). This treatment adjusts the SMN2 gene and lets it make more protein. It's used for both children and adults with SMA. Your child's medical team will inject the drug into the fluid around their spinal cord. Including preparation and recovery time, this can take at least 2 hours and will need to be done several times, followed by another dose every 4 months. Studies show it helps about 40% of people who use it by making them stronger and slowing the disease.
  • Onasemnogene abeparvovec-xioi (Zolgensma). This involves replacing the problem SMN1 gene. It's used for children under 2 years old. Your child's medical team will put a tiny tube called a catheter directly into a vein in their arm or hand (an IV). Then, they'll send a copy of the SMN gene through the tube into a specific group of motor neuron cells. This will need to be done only one time. In studies, onasemnogene abeparvovec-xioi helped children with SMA reach certain developmental milestones faster, like controlling their heads or sitting without support.
  • Risdiplam (Evrysdi). This treatment works to stop the SMN2 genes from disrupting the protein production,  allowing the protein to reach the nerve cells as needed. Your child takes it orally once a day after a meal. The dosage is determined by their weight.Clinical trials showed improved muscle function after 12 months in 41% of those taking it.

What are the risk factors for spinal muscular atrophy type iii?

SMA is a disease that's passed down through families. If your child has SMA, it's because they have two copies of a broken gene, one from each parent.

Is there a cure/medications for spinal muscular atrophy type iii?

Spinal muscular atrophy type iii, a rare hereditary disorder characterised by the progressive loss of motor neurons-the nerve cells that regulate voluntary movement-causes muscle weakness and wasting. Type 3 is a milder type of SMA.

Although there is currently no cure for SMA type 3, since 2016 there have been medicines that can delay or even stop the disease's main forms from progressing.


  • SMA type 3 can be treated with a variety of drugs as well as different types of physical therapy to increase strength and maintain motor function.
  • The U.S. Food and Drug Administration (FDA) has only approved Spinraza (nusinersen) as of August 2020 as a treatment for various kinds of SMA in both adults and children.
  • For persons with SMA, spinraza is thought to boost the amount of surviving motor neuron protein.
  • Seven out of seven SMA type 3 patients in one treatment trial "achieved considerable improvements in their walking capacity".

Mild muscle weakness,Difficulty walking and frequent respiratory infections,Poor balance,Frequent slips and falls,Needing help to stand up,Fatigue,Less endurance during activity,Poor or worsening posture,Clumsiness,Breathing Problems
Neuromuscular disease,Weak muscles
Spinraza (nusinersen),Evrysdi,Zolgensma

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