Spinal Muscular Atrophy (SMA)

Guidance for primary care clinicians receiving a positive newborn screen result

Other Names

SMA SMA type I
SMA type II
SMA type III
SMA type IV

ICD-10 Coding

G12.9, Spinal muscular atrophy, unspecified

Disorder Category

Musculoskeletal disease


Abnormal Finding

Homozygous deletion of the SMN1 gene

Tested By

Real-time PCR


Spinal muscular atrophy (SMA) is a group of inherited conditions that affects the motor neurons of the spinal cord causing muscle weakness. Symptoms include difficulty crawling, walking, breathing, swallowing, and controlling the head and neck. There are several types of SMA; classification is based on the severity of the condition and the age at which symptoms begin. Early detection and treatment are most effective when started early.

The long-term outlook varies significantly based on the type, symptoms, and response to treatment. The more severe types of SMA are associated with a shortened lifespan. Newer therapies may improve survival. In general, infants with SMA type I die in early childhood. Those affected by SMA type II live into adolescence and early adulthood. Most people with type III have a normal lifespan but are more susceptible to respiratory infections. SMA type IV is associated with a normal life expectancy.

Clinical Characteristics

Newborns with SMA will usually be asymptomatic. Those with Type 1 may develop apparent hypotonia within weeks of birth. Newborns with the rare Type 0 will be severely hypotonic at birth and have contractures, swallowing problems, and respiratory failure.


The incidence of SMA is approximately 1 in 12,500. [Verhaart: 2017]


Autosomal recessive

Primary Care Management

Next Steps After a Positive Screen

  • Contact family regarding the need for evaluation and additional testing.

Confirming the Diagnosis

If the Diagnosis is Confirmed

  • Educate the family regarding signs, symptoms, and the need for specialized care.
  • Urgent treatment and follow-up should be continued as indicated by pediatric neurology.
  • For those identified after onset of symptoms, therapy is still beneficial and should be started.


Information & Support

Related Portal Content
Spinal Muscular Atrophy
Assessment and management information for the primary care clinician caring for the child with spinal muscular atrophy.
Spinal Muscular Atrophy (FAQ)
Answers to questions families often have about caring for their child with spinal muscular atrophy.
After a Diagnosis or Problem is Identified
Families can face a big change when their baby tests positive for a newborn condition. Find information about A New Diagnosis - You Are Not Alone; Caring for Children with Special Health Care Needs; Assistance in Choosing Providers; Partnering with Healthcare Providers; Top Ten Things to Do After a Diagnosis.


ACT Sheet for Spinal Muscular Atrophy (ACMG) (PDF Document 157 KB)
Contains short-term recommendations for clinical follow-up of the newborn who has screened positive; American College of Medical Genetics.

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Authors & Reviewers

Initial publication: June 2019
Current Authors and Reviewers:
Author: Kimberly Hart, MS, LCGC
Reviewer: Russell Butterfield, MD, PhD

Page Bibliography

Verhaart IEC, Robertson A, Wilson IJ, Aartsma-Rus A, Cameron S, Jones CC, Cook SF, Lochmüller H.
Prevalence, incidence and carrier frequency of 5q-linked spinal muscular atrophy - a literature review.
Orphanet J Rare Dis. 2017;12(1):124. PubMed abstract / Full Text