ALS Genetics & Gene Carriers

I Have ALS: Genetic Testing and What It Can Mean

A genetic test may identify a genetic cause or contributor to ALS even when there is no known family history of the disease.

  • help explain the genetic basis of ALS
  • identify implications for biological relatives
  • identify eligibility for a gene-targeted treatment
  • identify eligibility for gene-specific research or clinical trials

Sources: Genetic Testing Information Sheet · Evidence-Based Consensus Guidelines for ALS Genetic Testing and Counseling

Genetic testing and counseling

Genetic counseling is an important part of ALS genetic testing.

A genetic counselor or appropriately trained clinician can review:

  • personal and family history
  • what a genetic test can and cannot answer
  • possible results
  • implications for relatives
  • psychological considerations
  • privacy and insurance considerations
  • reproductive considerations where relevant

Genetic counseling does not require a person to proceed with testing.

Expert consensus recommends that all people diagnosed with ALS be offered genetic testing.

Sources: Evidence-Based Consensus Guidelines for ALS Genetic Testing and Counseling · Genetic Counseling

Understanding positive, negative, and VUS results

Family implications

A genetic result can provide information that is relevant beyond the person diagnosed with ALS.

Many major ALS-associated genes are inherited in an autosomal dominant pattern. In an autosomal dominant condition, a person who carries a pathogenic variant may have a 50% chance of passing that variant to each biological child.

Inheritance is not the same as penetrance.

A person may inherit a disease-associated variant without necessarily developing ALS.

Risk depends on:

  • the specific gene
  • the specific variant
  • age
  • penetrance
  • family history
  • other genetic or environmental modifiers that may not yet be fully understood

Sources: Amyotrophic Lateral Sclerosis Overview · C9orf72 Frontotemporal Dementia and/or Amyotrophic Lateral Sclerosis

Gene-specific treatments and trials

Genetic testing can directly affect treatment or research options.

The clearest current example is SOD1-associated ALS.

QALSODY (tofersen) is FDA-approved for adults with ALS associated with a mutation in SOD1.

The FDA approved tofersen through the accelerated approval pathway based on reduction in plasma neurofilament light, a biomarker of nerve injury.

Gene-targeted research is ongoing for other forms of genetic ALS. Availability changes over time.

Search ALS studies on ClinicalTrials.gov

Sources: FDA approves treatment of ALS associated with a mutation in the SOD1 gene

Sources & Further Reading

These source cards link directly to the original material. External websites open in a new tab.

This information is for education and does not replace individualized medical advice, genetic counseling, diagnosis, or treatment. Genetic risk, penetrance, and testing implications can differ by gene, variant, family, and individual.

Last reviewed: 09-30-2026

Medical information should be reviewed periodically as genetic research and clinical trials change.