Intestinal Transporter and Enzyme Disorders

Intestinal transporter and enzyme disorders are genetic diseases of the intestine that cause diarrhea and an inability to absorb nutrients. In these disorders, even though the structure of the intestine may be normal, a patient may have trouble managing certain nutrients. This is because key proteins that carry nutrients across the intestine are missing or do not function properly. Some patients can be missing enzymes that allow specific nutrients to be digested properly.

Examples may include:

• Sucrase isomaltase deficiency
• Congenital chloride diarrhea
• Glucose-galactose malabsorption
• Congenital sodium diarrhea

Infants and children with these disorders, termed congenital diarrheas, may need specialized nutrition such as glucose and galactose-free formula or intravenous nutrition in order to grow normally.

Disorders involving intestinal nutrient transporters and enzymes often result in severe diarrhea. Signs of intestinal transport and enzyme disorders can appear after birth or after a child first starts feeding. Nutrients, such as carbohydrates or fats, need to be broken down by specific enzymes before being absorbed by the intestine and need special nutrient transporters to move across the lining of the intestine.

Each enzyme or transporter is specific for a certain kind of nutrient, and if they don’t work properly or are missing, they result in diarrhea.

Testing for these involves a number of steps. First doctors will test to determine the kind of diarrhea involved and which nutrients cannot be absorbed. If they suspect one of these disorders they may recommend a trial of a specialized formula. They will also need to look at a sample of the tissue in the small intestine. To do this they will need to perform a procedure called an endoscopy — a procedure which uses a small flexible viewing tube to look at the intestine and obtain tiny tissue samples (biopsies).

One of the main ways of diagnosing these disorders is through genetic testing to see whether there are any differences in the genes known to cause intestinal transporter and enzyme disorders.

There are a variety of nutritional therapies for these disorders including specialized formulas and parenteral nutrition. Before introducing proper treatment, first we need to find out which nutrient is involved. We accomplish this by introducing different dietary challenges.

To determine which nutrient is involved, we may remove the nutrient from the child’s formula or diet. Sometimes we will need to provide nutrition directly using intravenous line (IV) nutrition. Our focus of treatment revolves around long-term maintenance of nutrition and optimizing growth and development.

The Boston Children’s Hospital Division of Gastroenterology, Hepatology and Nutrition has extensive experience in the caring for children with all types of intestinal transporter and enzyme disorders. Our congenital enteropathy team works closely with multiple specialties, including the Home Parenteral Nutrition Program, to provide expert, family centered care for infants, children, and adolescents.