Spinal Muscular Atrophy

Introduction

The Questions and Answers that follow aim to provide an introduction to spinal muscular atrophy (SMA) for parents and other family members. Following those, we offer links to selected resources for more information and support and a list of valuable services.
More information about many topics relevant to children with SMA and many other chronic conditions and their families can be found in the left menu. Detailed information aimed at primary care doctors can be found in our in Spinal Muscular Atrophy module.

What is spinal muscular atrophy?

Spinal muscular atrophy (SMA) is an inherited disorder that causes early death of motor neurons leading to loss of muscle strength. Motor neurons are nerve cells in the spinal cord that are involved in swallowing, sleeping, and breathing. The loss of these cells can have a major impact on a person’s body, causing them to have difficulties with basic functions of life, like eating and breathing.

How do you get SMA?

SMA is caused by mutations or changes in two genes: SMN1 and SMN2, which then cause proteins to be defective or not produced (see Causes/Inheritance of SMA for more information). The condition is inherited as a recessive trait, meaning that parents can be carriers without having the disorder themselves. When a child inherits the recessive gene from both parents, the child will have SMA. It is estimated that 1 in 40 to 1 in 60 people are carriers of SMA.

What are the symptoms?

There is a spectrum of how severely children with SMA are affected. Symptoms will depend on the SMA subtype and the patient’s age. The most common symptoms are muscle weakness, trouble breathing, and loss of motor skills.
Infants with severe SMA are very weak and have difficulty swallowing and breathing. SMA may also be diagnosed in toddlers and even older children based on the appearance of muscle weakness with normal intellectual ability.
Getting treatment may prevent the loss of motor neurons and stop the progression of the condition. Children who get treatment may show fewer or no symptoms, and may regain some lost motor skills. It is important to get treatment as soon as possible.

How is it diagnosed?

SMA is suspected by a patient’s history and presentation, but diagnosed by genetic testing. A blood test is used to screen for the mutation in the SMN1 gene. A neurologist may be involved in the diagnosis.
Many states now include a test for SMA as part of routine newborn screening, which makes it easier to find and treat children with SMA.

What is the expected outcome?

The outcome will depend on how quickly a child receives treatment, as well as the severity (or subtype) of SMA. Getting a correct diagnosis and receiving treatment as soon as possible may prevent the loss of motor neurons, stop the progression of the condition, and improve outcomes.
For children who do not receive treatment, therapies such as feeding tubes and respiratory support are usually necessary to prevent death. Infants who show symptoms of SMA will often have difficulty with swallowing and breathing. Toddlers and young children may learn to sit and walk but may also have respiratory and swallowing difficulties leading to a shortened life span.
It is vital to start treatment as soon as possible after a child shows symptoms. Early treatment may prevent loss of motor skills.
Children who are older and have already lost motor neurons may also be able to regain some motor skills after treatment. These may be small milestones, such as greater ability to move a hand or finger. Some older children or adults do not see improvements in motor skills after treatment, but receiving treatment stops the progression of the condition.

Will anyone else in the family get SMA?

SMA is an inherited, recessive condition. That means if parents have a child with this condition, both parents are carriers of the abnormal gene and for each subsequent pregnancy there is a
  • 1 in 4 chance of the child having the condition
  • 2 in 4 chance of the child being a carrier
  • 1 in 4 chance of the child not having the gene mutation or the disorder
Talk to your doctor if you have concerns about muscle weakness in other children, because it is possible that other children also have the condition. While most families only have one child with SMA, some have multiple children with the condition. It is possible to have a child with SMA even if there is no history of the condition on either side of the family.

What is the treatment?

SMA is a complicated medical condition and in the past there was no treatment for the underlying genetic cause. There are now two treatments available, with others being tested. These medications are:
  • Zolgensma – a gene therapy used to treat children under age 2. It is a one-time treatment that works on replacing the function of the SMN1 gene, causing it to make the correct protein.
  • Spinraza – a gene therapy used to treat people of any age. It is given by lumbar puncture; first in a loading phase, then every four months for the rest of the person’s life. It works on the SMN2 gene, causing it to make a more complete protein.
These medications may be very expensive, though many insurance companies are providing coverage for them. Case support managers who work for the drug company may be available to work with families in the US who have trouble getting their health insurer to cover the treatment. To be optimally effective, treatment must begin as soon as possible after diagnosis. Some states are using, or considering, newborn screening programs to identify children in the first several days of life. Once the diagnosis is suspected, specialists will discuss medication with parents and get the treatment process started.
There are also many therapies available to help with symptoms, such as range of motion exercises and help with ambulation. Your child should be seen regularly by doctors familiar with SMA, including pulmonologists and neurologists. Your child may also need to see an occupational therapist and a physical therapist depending on his symptoms.

How will my family’s life be changed?

The impact on the family will depend on how quickly a child receives treatment, as well as the severity of the disease. With early diagnosis and treatment, outcomes have improved and families are able to help their children live full lives. While long-term studies of treatment are not yet available, in many cases, infants who would not have lived past 2 years old are surviving longer with relatively good health.
Older children diagnosed with SMA may have problems including difficulty sitting, difficulty walking, scoliosis, and respiratory or swallowing problems.

I would like to meet other families who have a child with SMA. How can I find them?

There are several family support organizations to help you connect with other families. These include Cure SMA, SMA Support Inc., and others.

My child's doctor says she needs medical equipment but my insurance won't pay for it. What can I do?

Talk to your child's doctor about the denial from insurance. The doctor can write a letter of medical necessity (for information see Writing Letters of Medical Necessity) and request reconsideration. Cure SMA also has an equipment loaning service that might be helpful. To access this service, see the website or email equipment@curesma.org

What does the future hold for people with SMA?

With two treatments available, a third in clinical trials, and others being researched, there are reasons to be hopeful. Outcomes are improved with treatment, and children can live full lives. Many accommodations can be made to help children and adults with SMA reach their greatest potential. There is a lot of support available for people with SMA and their families.

Resources

Information & Support

Where can I go for further information?

For Parents and Patients

Support

Cure SMA
Offers information about research in SMA, access to support and local chapters, and opportunities for fundraising.

SMA Support Inc.
Online information, family support, and research fund-raising

General

Spinal Muscular Atrophy (MedlinePlus)
Excellent, detailed review of condition for patients and families; National Library of Medicine and National Institutes of Health.

Spinal Muscular Atrophy (MedlinePlus)
A brief description of SMA, along with numerous links to further information; sponsored by the National Library of Medicine.

SMA Coalition
A coalition of SMA-focused nonprofits working toward increased awareness and help for those with SMA.

Spinal Muscular Atrophy (GeneReviews)
An expert-authored, peer-reviewed, current disease description that applies genetic testing to diagnosis and management information; U.S. National Library of Medicine.

Genetics in Primary Care Institute (AAP)
Contains health supervision guidelines and other useful resources for the care of children with genetic disorders; American Academy of Pediatrics.

Services for Patients & Families in Nevada (NV)

For services not listed above, browse our Services categories or search our database.

* number of provider listings may vary by how states categorize services, whether providers are listed by organization or individual, how services are organized in the state, and other factors; Nationwide (NW) providers are generally limited to web-based services, provider locator services, and organizations that serve children from across the nation.

Authors & Reviewers

Initial publication: October 2012; last update/revision: July 2020
Current Authors and Reviewers:
Author: Lynne M. Kerr, MD, PhD
Reviewer: Angel Wolff
Funding: The Medical Home Portal thanks the 2011-2012 URLEND Medical Home Portal trainees group for their contribution to this page.
Authoring history
2016: first version: Meghan Candee, MDR
AAuthor; CAContributing Author; SASenior Author; RReviewer