Glucose Galactose Malabsorption (GGM)

Glucose galactose malabsorption, also known as GGM, is a genetic condition in which a child’s body cannot absorb the simple sugars glucose and galactose. This can lead to severe and chronic diarrhea when the child consumes these substances. Glucose galactose malabsorption is very rare, and a only few hundred cases have been reported worldwide.

Glucose galactose malabsorption causes symptoms when a child ingests the sugars glucose or galactose. The primary symptom is severe diarrhea, which can lead to dehydration and weight loss that may become life threatening. Diarrhea tends to begin when the infant is fed breast milk or commercial formula.

Rarely, some babies with glucose galactose malabsorption may also develop kidney stones.

Glucose galactose malabsorption is caused by mutations in the SLC5A1 gene. This gene is responsible for helping the body produce a protein found in the gastrointestinal tract and kidneys. This protein helps the body absorb glucose and galactose.

When your child has a mutation in the SLC5A1 gene, they can’t absorb glucose and galactose. Instead, these sugars remain in the intestinal tract, along with water that would have been absorbed with them. This can result in severe diarrhea and dehydration.

The parents of a child with glucose galactose malabsorption each carry one copy of the mutated gene but don’t usually have symptoms of the condition themselves.

Clinicians may suspect glucose galactose malabsorption if your child develops severe diarrhea early in life. If symptoms improve in the absence of glucose and galactose — and if other causes of diarrhea are ruled out — your child may have glucose galactose malabsorption. Genetic testing can confirm the diagnosis.

Treatment for glucose galactose malabsorption involves avoidance of glucose and galactose and foods that contain them. Infants may require formula that contains fructose, another type of sugar. Although it’s not clear why, some children with glucose galactose malabsorption may be able to tolerate increasing amounts of these sugars as they get older.

At Boston Children’s Hospital, we care for children with glucose galactose malabsorption in our Congenital Enteropathy Program — one of just a few centers in the world that specializes in congenital diarrhea. We care for children with severe diarrhea who may have had multiple previous tests that failed to identify a cause, and who may have been hospitalized because of severe dehydration and malnutrition.