What are the other Names for this Condition? (Also known as/Synonyms)

• Congenital Sucrose-Isomaltase Malabsorption
• Disaccharide Intolerance, 1
• SI Deficiency Disorder

What is Congenital Sucrase-Isomaltase Deficiency Disorder? (Definition/Background Information)

• Congenital Sucrase-Isomaltase Deficiency (CSID) Disorder is a genetic condition that affects a person's ability to digest certain sugars
• People with this condition cannot break down the sugars sucrose (a sugar found in fruits, and also known as table sugar) and maltose (the sugar found in grains)
• Congenital Sucrase-Isomaltase Deficiency Disorder usually becomes apparent after an infant begins to consume fruits, juices, and grains
• After ingestion of sucrose or maltose, an affected child will typically experience stomach cramps, bloating, excess gas production, and diarrhea. These digestive problems can lead to failure to thrive and malnutrition
• Most affected children are better able to tolerate sucrose and maltose as they get older
• Congenital Sucrase-Isomaltase Deficiency Disorder is inherited in an autosomal recessive pattern and is caused by mutations in the SI gene

(Source: Congenital Sucrase-Isomaltase Deficiency; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

Who gets Congenital Sucrase-Isomaltase Deficiency Disorder? (Age and Sex Distribution)

• Congenital Sucrase-Isomaltase Deficiency Disorder is a rare congenital disorder. The symptoms of the disorder may be noticed after 6 months, when the infant is generally given foods other than breastmilk
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Congenital Sucrase-Isomaltase Deficiency Disorder? (Predisposing Factors)

• A positive family history may be an important risk factor, since Congenital Sucrase-Isomaltase Deficiency Disorder can be inherited
• Currently, no risk factors have been clearly identified for this deficiency disorder

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Congenital Sucrase-Isomaltase Deficiency Disorder? (Etiology)

• Congenital Sucrase-Isomaltase Deficiency Disorder is a genetic disorder that involves mutations on the SI gene
• The condition is transmitted in an autosomal recessive manner

Autosomal recessive inheritance: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Congenital Sucrase-Isomaltase Deficiency Disorder?

Affected infants usually develop symptoms soon after they first ingest sucrose, which is found in modified milk formulas, fruits, or starches. Symptoms may include explosive, watery diarrhea resulting in abnormally low levels of body fluids (dehydration), abdominal swelling (distension), and/or abdominal discomfort. In addition, some affected infants may experience malnutrition, resulting from malabsorption of essential nutrients, and/or failure to thrive, resulting from nutritional deficiencies. In some cases, individuals may exhibit irritability; colic; abrasion and/or irritation (excoriation) of the skin on the buttocks as a result of prolonged diarrhea episodes; and/or vomiting.

Symptoms of Congenital Sucrase-Isomaltase Deficiency Disorder vary among affected individuals, but are usually more severe in infants and young children than in adults. Symptoms exhibited in infants and young children are usually more pronounced than those of the affected adults because the diet of younger individuals often includes a higher carbohydrate intake. In addition, the time it takes for intestinal digestion is less in infants or young children.

The signs and symptoms of Congenital Sucrase-Isomaltase Deficiency Disorder may include:

• Abnormality of metabolism/homeostasis
• Autosomal recessive inheritance
• Malabsorption
• Nephrolithiasis
• Very frequently present symptoms in 80-99% of the cases may include diarrhea.
• Frequently present symptoms in 30-79% of the cases may include vomiting.
• Occasionally present symptoms in 5-29% of the cases:
  • Abdominal colic
  • Abdominal distention

(Source: Congenital Sucrase-Isomaltase Deficiency; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How is Congenital Sucrase-Isomaltase Deficiency Disorder Diagnosed?

• Congenital Sucrase-Isomaltase Deficiency Disorder can be diagnosed by taking a small sample of tissue (biopsy) from the small intestine for a specific test known as a disaccharidase assay
• Other tests may include a sucrose hydrogen breath test in which an abnormally high level of hydrogen will be detected in the breath of an affected individual after sucrose ingestion
• Genetic testing may be indicated in some cases.

(Source: Congenital Sucrase-Isomaltase Deficiency; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Congenital Sucrase-Isomaltase Deficiency Disorder?

The complications of Congenital Sucrase-Isomaltase Deficiency Disorder may include:

• Severe malnutrition in young children
• Failure to thrive

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Congenital Sucrase-Isomaltase Deficiency Disorder Treated?

• Congenital Sucrase-Isomaltase Deficiency Disorder is typically treated by modifying a person's diet to reduce the amount of sucrose
• Because many foods contain sucrose and other complex sugars, it can be difficult to completely remove sucrase from the diet
• Sucraid is an oral medication containing the enzyme that does not work properly in people with this condition

By taking this medication, those with CSID Disorder can eat sucrose-containing foods because this enzyme will break down sucrose. This medication must be taken with each meal or snack.

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of CSID Disorder:

• Sacrosidase (or Sucraid®)
• FDA-approved indication: Oral replacement therapy of the genetically determined sucrase deficiency, which is part of congenital sucrease-isomaltase deficiency.

(Source: Congenital Sucrase-Isomaltase Deficiency; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How can Congenital Sucrase-Isomaltase Deficiency Disorder be Prevented?

Currently, Congenital Sucrase-Isomaltase Deficiency Disorder may not be preventable, since it is a genetic disorder.

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

Regular medical screening at periodic intervals with tests and physical examinations are recommended.

What is the Prognosis of Congenital Sucrase-Isomaltase Deficiency Disorder? (Outcomes/Resolutions)

• The prognosis of Congenital Sucrase-Isomaltase Deficiency Disorder is dependent upon the severity of the signs and symptoms and associated complications, if any
• Individuals with mild conditions have better prognosis than those with severe symptoms and complications
• Typically, the prognosis may be assessed on a case-by-case basis

Additional and Relevant Useful Information for Congenital Sucrase-Isomaltase Deficiency Disorder:

Congenital Sucrase-Isomaltase Deficiency is also known by the following names: 

• Congenital Sucrose Intolerance
• CSID Disorder

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/