Is Congenital Sucrase Isomaltase Deficiency hereditary?

Congenital Sucrase Isomaltase Deficiency (CSID) is a hereditary genetic condition caused by mutations in the SI gene. It follows an autosomal recessive inheritance pattern, meaning an individual must inherit two copies of the mutated gene—one from each parent—to manifest the disorder.

Is Congenital Sucrase Isomaltase Deficiency hereditary?

Yes, Congenital Sucrase Isomaltase Deficiency is strictly a hereditary condition, not an acquired one. Being hereditary means the genetic mutations responsible for the enzyme deficiency are passed down through families. While "genetic" refers to the presence of a mutation, "hereditary" confirms that these mutations are inherited from parents who are typically asymptomatic carriers.

What is the inheritance pattern of Congenital Sucrase Isomaltase Deficiency?

Congenital Sucrase Isomaltase Deficiency follows an autosomal recessive inheritance pattern. If both parents are carriers of a pathogenic variant in the SI gene, the risks for each pregnancy are as follows:

• 25% chance the child will have Congenital Sucrase Isomaltase Deficiency.


• 50% chance the child will be an asymptomatic carrier.


• 25% chance the child will not inherit any mutation.

De novo (spontaneous) mutations are extremely rare in Congenital Sucrase Isomaltase Deficiency; the vast majority of cases are inherited from parents who carry the recessive trait.

How is genetic testing used for diagnosis?

Genetic testing via molecular analysis of the SI gene is the gold standard for confirming a diagnosis of Congenital Sucrase Isomaltase Deficiency. While clinicians often use breath testing or disaccharidase activity assays from small bowel biopsies, genetic testing provides definitive evidence of the underlying molecular defect. We recommend genetic counseling for families to interpret these results and understand the implications for siblings and future children.

Next steps

• Consult with a clinical geneticist to discuss testing options for family members.


• Connect with the 140 members of the Congenital Sucrase Isomaltase Deficiency community on DiseaseMaps.org to share experiences.


• Request a referral to a metabolic specialist or gastroenterologist familiar with rare carbohydrate malabsorption syndromes.

Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Congenital sucrase-isomaltase deficiency.


• OMIM (Online Mendelian Inheritance in Man): Sucrase-Isomaltase Deficiency (#222900).


• Orphanet: Congenital sucrase-isomaltase deficiency.


• PubMed/NCBI: Clinical and genetic spectrum of SI gene mutations.