Glucose-galactose malabsorption

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Glucose-galactose malabsorption is a condition in which the body cannot take in (absorb) the sugars glucose and galactose, which primarily results in severe diarrhea. Beginning in infancy, severe diarrhea results in weight loss and dehydration that can be life-threatening. Small amounts of the simple sugar glucose in the urine (mild glucosuria) may occur in this disorder. Rarely, affected infants develop kidney stones due to deposits of calcium in the kidneys (nephrocalcinosis).

The signs and symptoms of glucose-galactose malabsorption appear early in life when affected infants are fed breast milk or regular infant formulas. These foods contain glucose, galactose, and another sugar called lactose that gets broken down into these two sugars. When these sugar-containing foods are ingested by affected individuals, it leads to diarrhea and other health problems. If foods that contain glucose, galactose, and lactose are removed from the diet, the diarrhea stops.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in the SLC5A1 gene cause glucose-galactose malabsorption. The SLC5A1 gene provides instructions for producing a protein called sodium/glucose cotransporter protein 1 (SGLT1). This protein is found mainly in the intestinal tract and the kidneys. It spans the membrane of cells in these body systems and moves (transports) glucose and galactose from outside the cell to inside the cell. Sodium and water are transported across the cell membrane along with the sugars in this process. Glucose and galactose are simple sugars; they are present in many foods, or they can be obtained from the breakdown of lactose or other sugars and carbohydrates in the diet during digestion.

In the intestinal tract, the SGLT1 protein helps the body absorb glucose and galactose from the diet so the body can use them. During the digestion of food, the protein transports the sugars into the cells that line the wall of the intestine (intestinal epithelial cells) as food passes through.

The SGLT1 protein in kidney cells plays a role in maintaining normal blood glucose levels. The kidneys filter waste products from the blood and eliminate them in urine. They also reabsorb needed nutrients and release them back into the blood. The SGLT1 protein transports glucose into specialized kidney cells, ensuring that the sugar goes back into the bloodstream and is not released into the urine.

SLC5A1 gene mutations impair or eliminate the function of the SGLT1 protein. As a result, glucose and galactose are not absorbed by intestinal epithelial cells but instead accumulate in the intestinal tract. In addition, water that normally would have been transported with the sugars remains in the intestinal tract, resulting in dehydration of the body's tissues and severe diarrhea. The SGLT1 protein in kidney cells cannot transport glucose; however, other proteins in the kidneys are able to absorb enough glucose into the bloodstream, so that glucosuria is mild, if present at all, in people with glucose-galactose malabsorption.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Glucose-galactose malabsorption is a rare disorder; only a few hundred cases have been identified worldwide. However, as many as 10 percent of the population may have a somewhat reduced capacity for glucose absorption without associated health problems.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Diarrhea · Very frequent (99-80%)

Abnormally increased frequency (usually defined as three or more) loose or watery bowel movements a day.

Failure to thrive · Very frequent (99-80%)

Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm.

Osmotic diarrhea · Very frequent (99-80%)

Osmotic diarrhea results from the presence of osmotically active, poorly absorbed solutes in the bowel lumen that inhibit normal water and electrolyte absorption.

Weight loss · Very frequent (99-80%)

Reduction of total body weight.

Dehydration · Very frequent (99-80%)

Abdominal distention · Frequent (79-30%)

Distention of the abdomen.

Hypernatremia · Frequent (79-30%)

The concentration of sodium in the blood circulation is above the upper limit of normal.

Malnutrition · Frequent (79-30%)

A deficiency in the intake of energy and nutrients.

Other findings in the same source

From: Orphanet

Additional reported features include Hyperactive bowel sounds (Occasional (29-5%)); Hypercalcemia (Occasional (29-5%)); Nephrolithiasis (Occasional (29-5%)); Renal insufficiency (Occasional (29-5%)); Vomiting (Occasional (29-5%)); Fever (Very rare (<4-1%)); Hematuria (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Glucose-galactose malabsorption is Gastroenterology, with a gastroenterologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which digestive symptoms or nutritional changes matter most?
• What question would an endoscopy, scan or laboratory test answer if one is proposed?
• How should persistent pain, bleeding or difficulty eating be followed up?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Glucose-galactose malabsorption. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.