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People with the MS genotype do not have alpha-1 antitrypsin deficiency, but are genetic carriers of the S mutation. There is no known increased risk for lung or liver disease associated with the MS genotype. The S mutation is known to cause a moderate reduction in the quantity of alpha-1 antitrypsin (AAT), and can contribute to AATD in people who have two AATD mutations (e.g. SZ).

Because Alpha-1 is a genetic condition, your result means that your relatives are at increased risk to also have abnormal alpha-1 genes. We encourage you to make your family members and any reproductive partner aware of your result and the availability of testing. Testing for relatives must look for the S mutation to ensure accurate results. Reproductive partners of people with abnormal alpha-1 genes should be offered testing to assess risk to children.

Alpha-1 at MUSC – Genetic Counseling

S: mild variant
• more common than the Z allele
• doesn’t get trapped in the liver – not typically associated with liver disease
• originated in the Iberian Peninsula (Spain and Portugal)
• low estimate that 5% (possibly as high as 12%) of North Americans are MS

What is Your Phenotype and What Does it Mean? – Kimberly Foil, MS, CGC, Genetic Counseling Program, Alpha-1 Foundation; Division of PulmonaryMedical term referring to the lungs. and Critical Care Medicine, Medical University of South Carolina (MUSC)