Spinal Muscular Atrophy (SMA)Symptoms, Doctors, Treatments, Advances & More
Learn About Spinal Muscular Atrophy (SMA)
Spinal muscular atrophy (SMA) is a group of diseases of the motor neurons (motor cells). These diseases are passed down through families (inherited) and can appear at any stage of life. They lead to muscle weakness and atrophy.
Werdnig-Hoffmann disease; Kugelberg-Welander disease
SMA is a collection of different motor nerve (or neuron) diseases. The disease is caused by a lack of a protein due to a variant survival motor neuron (SMN) gene.
Most of the time, a person must get one copy of the variant gene from both parents to be affected. The most severe form is SMA type I, also called Werdnig-Hoffman disease. Infants with SMA type II have less severe symptoms during early infancy, but they become weaker with time. SMA type III is also known as Kugelberg-Welander disease, a less severe form of the condition.
In rare cases, SMA begins in adulthood. This is the mildest form of the disease.
A family history of SMA in an immediate family member (such as a brother or a sister) is a risk factor for all types of the disorder.
Symptoms of SMA may vary depending on the SMA type.
- Infants with SMA type I are born with very little muscle tone, weak muscles, and feeding and breathing problems.
- In infants with SMA type II, symptoms may not appear until age 6 to 18 months.
- Type III SMA is a milder disease that starts in childhood or adolescence and slowly gets worse.
- Type IV is even milder, with weakness starting in adulthood.
Often, weakness is first felt in the shoulder and leg muscles. Weakness gets worse over time and eventually becomes severe.
Symptoms in an infant:
- Breathing difficulty with shortness of breath and labored breathing, leading to a lack of oxygen
- Feeding difficulty (food may go into the windpipe instead of the stomach)
- Floppy infant (poor muscle tone)
- Lack of head control
- Little movement
- Weakness that gets worse
Symptoms in a child:
- Frequent, increasingly severe respiratory infections
- Nasal speech
- Posture that gets worse
With SMA, the nerves that control feeling (sensory nerves) are not affected. So, a person with the disease can feel things normally.
There is no treatment to cure SMA. However, there are now three medicines approved by the FDA that slow how fast the muscle weakness progresses:
- Onasemnogene abeparvovec-xioi (Zolgensma)
- Risdiplam (Evrysdi)
- Nusinersen (Spinraza)
These medicines work by increasing the amount of the SMN protein produced. Talk with your provider to see if either of these medicines is right for you or your child.
Supportive care is important. Breathing complications are common in the more severe forms of SMA. To help with breathing, a device or machine called a ventilator may be needed.
People with SMA also need to be watched for choking. This is because the muscles that control swallowing are weak.
Physical therapy is important to prevent contractions of muscles and tendons and abnormal curvature of the spine (scoliosis). Bracing may be needed. Surgery may be needed to correct skeletal deformities, such as scoliosis.
UCLA Health Westwood Neurology
Perry Shieh is a Neurologist practicing medicine in Los Angeles, California. Dr. Shieh is rated as an Elite provider by MediFind in the treatment of Spinal Muscular Atrophy (SMA). He is also highly rated in 47 other conditions, according to our data. His clinical expertise encompasses Duchenne Muscular Dystrophy, Becker Muscular Dystrophy, Spinal Muscular Atrophy (SMA), and Tubular Aggregate Myopathy.
CUIMC/Harkness Pavilion
Claudia Chiriboga is a Pediatric Neurologist and a Neuromusculoskeletal Medicine provider practicing medicine in New York, New York. Dr. Chiriboga is rated as an Elite provider by MediFind in the treatment of Spinal Muscular Atrophy (SMA). She is also highly rated in 4 other conditions, according to our data. Her clinical expertise encompasses Spinal Muscular Atrophy (SMA), Primary Lateral Sclerosis, Spinal Muscular Atrophy Type 2, and Spinal Muscular Atrophy Type 1. Dr. Chiriboga is board certified in Neurology With Special Qualification In Child Neurology and Child Neurology. Dr. Chiriboga is currently accepting new patients.
Johns Hopkins Health Care & Surgery Center - Green Spring Station, Lutherville
Thomas Crawford is a Neurologist and a Pediatric Neurologist practicing medicine in Lutherville, Maryland. Dr. Crawford is rated as an Elite provider by MediFind in the treatment of Spinal Muscular Atrophy (SMA). He is also highly rated in 13 other conditions, according to our data. His clinical expertise encompasses Primary Lateral Sclerosis, Spinal Muscular Atrophy (SMA), Ataxia-Telangiectasia, and Spinal Muscular Atrophy Type 2. Dr. Crawford is board certified in American Board Of Psychiatry And Neurology and American Board Of Pediatrics. Dr. Crawford is currently accepting new patients.
Without treatment, children with SMA type I rarely live longer than 2 to 3 years because of respiratory problems and infections. Survival time with type II is longer, but the disease kills most of those who are affected while they are still children. New therapies that increase the amount of SMN protein have resulted in infants and children living much longer.
Children with type III disease may survive into early adulthood. But, people with all forms of the disease have weakness and disability that gets worse over time. Adults who develop SMA often have a normal life expectancy.
Complications that may result from SMA include:
- Aspiration (food and fluids get into the lungs, causing pneumonia)
- Contractions of muscles and tendons
- Heart failure
- Scoliosis
Contact your provider if your child:
- Appears weak
- Develops any other symptoms of SMA
- Has difficulty feeding
Breathing difficulty can rapidly become an emergency condition.
Genetic counseling is recommended for people with a family history of SMA who want to have children.
Summary: Because no long-term record of prenatal Spinal Muscular Atrophy (SMA) treatment exists, this study will address an important gap in the understanding of the safety and benefit of treatment while in the womb. The registry will help guide best practices for monitoring pregnant women and their fetus with SMA, if treated with a medication while in the womb, and to follow the baby after birth for signs...
Summary: This is an open-label, single-arm, multicenter clinical study to evaluate the effectiveness and safety of risdiplam administered as an early intervention in pediatric participants with spinal muscular atrophy (SMA) and 2 SMN2 copies who have previously received onasemnogene abeparvovec. Participants are children \< 2 years of age genetically diagnosed with SMA.
Published Date: October 27, 2025
Published By: Joseph V. Campellone, MD, Department of Neurology, Cooper Medical School at Rowan University, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Fearon C, Murray B, Mitsumoto H. Disorders of upper and lower motor neurons. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 97.
Manzur AY. Evaluation and investigation of neuromuscular disorders. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 647.
NIH-National Institute of Neurological Disorders and Stroke website. Spinal muscular atrophy. www.ninds.nih.gov/health-information/disorders/spinal-muscular-atrophy. Updated July 30, 2024. Accessed December 23, 2025.
Shaw PJ, Cudkowicz ME. Amyotrophic lateral sclerosis and other motor neuron diseases. In: Goldman L, Cooney K, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 387.