Spinal muscular atrophy 1 : Causes, Symptoms


In this blog, I will give you information regarding Spinal muscular atrophy type 1 disease. Its also called SMA1.

Spinal muscular atrophy is a neuromuscular disorder that results in the loss of motor neuron and progressive muscle wasting. So, patient having weakness in muscles of arm, leg & respiratory may affected first.

Spinal muscular atrophy may occur to any age of life. If SMA occurs within 6 months of child age, it is known as SMA 1. If this disease left untreated than it is most common genetic cause of infant death.

We learn this topic in below format


  • SMA1 occurs to infant at age of 0 to 6 months
  • In this disease child can not sit, stand or walk
  • It occurs to approx 1 child out of 10,000 birth. (1:10,000)
  • Earlier treatment is not available. After 2016, medicine is available named as Zolgensma injection marketed by novartis company. It cost approx $ 2.125 million. This medicine is costly due to below reasons

– single dose gene therapy

– Company need many scientist & staff for years to research new medicine. Which is too much costly.

– Company also needs fund for further research on different disease conditions.



Spinal muscular atrophy is linked to genetic mutation in the SMA1 gene.

It is autosomal recessive pattern of inheritance. If means mother & father is not suffering from disease but they are carrier of this disease. In that condition child may be born with SMA1 disease.

We have 23 pairs of chromosome. Out of that chromosome 5 having SMN1 gene. SMN1 means survival motor neuron 1 gene. This gene is required for survival of motor neuron which sends message from brain to body.

When child born with defect in SMN1 gene. In that condition motor neuron can not survive.

Motor neuron sends message from brain to our body. So, in spinal muscular atrophy 1 disease brain can not send proper message to our body. Due to that child can not sit, stand or walk & having many other problems.



  • Muscles weakness
  • Child can not hold his head
  • Can not sit, stand & walk
  • Tongue twitching
  • Difficulty in swallowing & feeding
  • Respiratory problems, so that child having problem in breathing.



SMA1 0 to 6 months can not sit
SMA2 6 to 18 months sit but can not stand
SMA3 after 1 year of age walk for sometime
SMA4 Occurs in adult minor symptoms



  • Doubt on basis of
    – less movement in later pregnancy
    – after delivery less movement & can not
  • Confirmed Diagnosis based on Genetic testing by blood report.



  • Zolgensma
  • Spinraza
  • Evrysdi


spinal muscular atrophy treatment
spinal muscular atrophy treatment

– Single dose therapy

– Cost approx $ 2.125 million. Other treatment therapy have 3 to 4 doses & total cost remains approximately same as above.

How zolgensma works?

This medicine enters virus AAV9 in patient’s body
Which takes place at defective or non functioning SMN1 gene
SMN1 gene increases SMN protein level
It improves motor neuron function & improves symptoms


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