Spinal Muscular Atrophy: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Spinal Muscular Atrophy?
A neurologist, a doctor who treats diseases of the nerves and brain, usually leads care for spinal muscular atrophy. Physical and occupational therapists can help too. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is spinal muscular atrophy?
Spinal muscular atrophy, or SMA, is a group of genetic diseases that damages and kills motor neurons. Motor neurons are nerve cells in the spinal cord and lower part of the brain. They control movement in the arms, legs, face, chest, throat, and tongue.
As motor neurons die, the muscles weaken and waste away. The damage gets worse over time and can affect speaking, walking, swallowing, and breathing. It affects about 1 in 8,000 to 10,000 people worldwide.
Symptoms
There are different types of SMA. They depend on how serious the disease is and when symptoms start.
- Type 1 is the most common and most severe type. Babies usually show signs before 6 months of age, with trouble swallowing and breathing and little movement.
- Type 2 is usually noticed between 6 and 18 months of age. Most children can sit without support but cannot stand or walk without help.
- Type 3 usually shows up after age 18 months. Children can walk but may have trouble running, getting up from a chair, or climbing stairs.
- Type 4 is rare and often mild. It causes mild to moderate leg weakness, tremors, and mild breathing problems.
Weakness is often worse in the chest and in the upper leg and arm muscles than in the hands and feet. People with SMA can also have lung infections, scoliosis (a curved spine), and joint contractures, which are shortened muscles and tendons.
Causes and who gets it
Most types of SMA are caused by a change in the SMN1 gene. This gene makes a protein that motor neurons need to stay healthy. When part of the gene is missing or abnormal, motor neurons die off.
SMA is passed down in an autosomal recessive pattern, which means both copies of the SMN1 gene have changes. A person who has only one changed copy is a carrier and will not have symptoms. Extra copies of a similar gene called SMN2 are linked to milder types.
How doctors diagnose it
A doctor takes a medical history, including family history, and does a physical exam. A blood test can look for changes in the SMN1 gene. Nerve and muscle tests may be done, especially if no gene changes were found. In some states, genetic testing for SMA is part of newborn screening. Parents with a family history of SMA can ask about a prenatal test.
Treatment
There is no cure for SMA. Several treatments protect motor neurons, improve muscle function, and extend lives, but they are not cures. Treatment early in life tends to help more than treatment later.
The FDA has approved these medicines:
- Nusinersen (Spinraza) increases SMN protein and is approved for children and adults.
- Onasemnogene abeparvovec (Zolgensma) is a gene therapy for children under two years old with infantile-onset SMA, or Type 1.
- Risdiplam (Evrysdi) is taken by mouth by people age two months and older.
Physical and occupational therapy can help posture and slow muscle weakness. Braces, orthotics, and wheelchairs can help people stay independent. Good nutrition matters, and some people need a feeding tube. Some people need breathing support, such as a device at night or a ventilator.
When to see a doctor
Call 911 or go to the emergency room if a person with SMA has severe trouble breathing, bluish or grey skin, or choking.
Families with a history of SMA can ask about genetic testing.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. Such a doctor can arrange a first evaluation and referral to a neurologist. They can also help coordinate therapy, nutrition, and breathing care over time.
Common questions
Is there a cure for SMA?
No, there is no cure for SMA. Treatments can help manage symptoms and prevent complications.
What causes SMA?
A change in the SMN1 gene causes most types of SMA. The gene change leaves too little of a protein that motor neurons need.
How is SMA passed down in families?
SMA is passed down when a child gets a changed SMN1 gene from both parents. A parent with one changed copy usually has no symptoms.
Is SMA life threatening?
It can be, depending on the type. Without treatment, many children with Type 1 will die before 2 years of age. People with Type 4 have a normal lifespan. Newer treatments are improving the expected course of the disease, especially for Types 1 and 2.
Can SMA be found before a baby is born?
Yes, a test during pregnancy can check for SMN1 gene changes. It uses a sample from amniocentesis or, in some cases, chorionic villi sampling.
Sources
- MedlinePlus - Spinal Muscular Atrophy
- National Institute of Neurological Disorders and Stroke - Spinal Muscular Atrophy
- MedlinePlus Genetics - Spinal muscular atrophy
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
