How common is sucrase deficiency?

December 4, 2025 •

5 min read

Sucrase deficiency, a condition impairing sugar digestion, is considered rare, affecting an estimated 1 in 5,000 people of European descent. However, this widely cited statistic does not capture the condition's full scope, as its true prevalence is complicated by ethnic variation, potential misdiagnosis, and both congenital and acquired forms.

Quick Summary

The prevalence of sucrase deficiency varies significantly across populations and can be congenital or acquired. The condition is often underdiagnosed due to symptom overlap with common GI disorders like IBS.

Key Points

Prevalence Varies Widely: Congenital sucrase deficiency is rare in most populations but is significantly more common among indigenous Arctic communities, where it can affect as many as 1 in 20 people.
Underdiagnosis is a Major Issue: Many cases are likely missed or misdiagnosed as other gastrointestinal conditions like Irritable Bowel Syndrome (IBS), obscuring the true commonness of sucrase deficiency.
Two Main Types Exist: Sucrase deficiency can be either congenital (genetic) or acquired (secondary) due to underlying damage or inflammation to the small intestine.
Symptomatic Carriers Affect Statistics: Individuals with a single faulty SI gene (heterozygous carriers) can also experience symptoms, further broadening the condition's impact beyond the classically defined genetic form.
Accurate Diagnosis is Difficult: Definitive diagnosis typically requires a small intestinal biopsy for a disaccharidase assay, a procedure that is invasive and not always the first step for patients with GI complaints.
Treatment is Manageable: Both dietary restrictions and enzyme replacement therapy with sacrosidase are effective treatment options for managing sucrase deficiency symptoms.

Understanding Sucrase Deficiency

Sucrase deficiency is a metabolic disorder resulting from insufficient activity of the sucrase-isomaltase (SI) enzyme complex in the small intestine. This enzyme is crucial for breaking down sugars such as sucrose (found in table sugar, fruits) and maltose (from starches) into simpler, absorbable sugars. When this process fails, undigested sugars move to the large intestine, where they are fermented by bacteria, causing a range of uncomfortable gastrointestinal symptoms.

What is the Sucrase-Isomaltase Enzyme?

The sucrase-isomaltase enzyme is a critical component of the intestinal brush border membrane. It is composed of two subunits: the sucrase subunit and the isomaltase subunit. The enzyme complex is responsible for digesting a variety of carbohydrates. A deficiency can impact the digestion of sucrose as well as maltose and other starch-derived sugars, though the impact on starch digestion varies depending on the specific genetic mutation and severity.

How Common Is Congenital Sucrase Deficiency?

Congenital sucrase-isomaltase deficiency (CSID) is the inherited form of the disorder, typically caused by mutations in the SI gene. The prevalence of CSID is not uniform globally, with striking differences observed between different ethnic and geographic groups.

Prevalence in European and General Populations

In populations of European descent, the classical form of CSID is estimated to affect approximately 1 in 5,000 individuals. Studies based on genetic analysis suggest the rate of homozygous or compound heterozygous carriers of pathogenic SI variants in European populations could be even lower, between 0.0005% and 0.013%. However, some clinical studies focusing on patients with gastrointestinal symptoms have reported higher rates of sucrase deficiency, sometimes over 9%, suggesting underdiagnosis is a significant issue.

High Prevalence in Arctic Populations

In stark contrast to global averages, CSID is significantly more common among indigenous populations in Arctic regions, including Greenland, Alaska, and Canada. Estimates suggest that as many as 1 in 20 people in these communities may be affected. Genetic studies have identified a specific founder mutation, SI c.273_274delAG, which is highly prevalent in these populations. This highlights how genetic factors can lead to dramatically different prevalence rates in isolated populations.

The Challenge of Diagnosing Sucrase Deficiency

One of the main reasons for the uncertainty surrounding how common sucrase deficiency is relates to diagnostic challenges. Symptoms of sucrase deficiency often overlap with more widely known gastrointestinal conditions, leading to frequent misdiagnosis.

Overlap with Other Conditions

Patients with sucrase deficiency may be misdiagnosed with a number of other conditions before the true cause is identified. The list of common overlapping diagnoses includes:

Irritable Bowel Syndrome (IBS), especially IBS with diarrhea (IBS-D)
Celiac disease
Lactose intolerance
Small intestinal bacterial overgrowth (SIBO)
Toddler's diarrhea

Why Is it Underdiagnosed?

Underdiagnosis is common because many healthcare providers are not familiar with sucrase deficiency, and the diagnostic process can be invasive or lack specificity. Breath tests are a less invasive screening tool but can produce false-negative results. The 'gold standard' for diagnosis is a disaccharidase assay on a small intestinal biopsy, which requires an endoscopy. The time-consuming and often inconclusive diagnostic journey can delay a correct diagnosis for years.

Acquired (Secondary) Sucrase Deficiency

In addition to the genetic form, sucrase deficiency can also be acquired, or secondary. This type is caused by damage to the lining of the small intestine, which impairs the production of the sucrase-isomaltase enzyme. Once the underlying cause is treated, the enzyme deficiency may resolve.

Common Causes of Secondary Deficiency

Celiac disease: The inflammatory response damages the intestinal villi, where the enzyme is located.
Gastroenteritis: Viral or bacterial infections can cause temporary damage.
Crohn's disease: Chronic inflammation in the digestive tract leads to mucosal damage.
Medications: Certain drugs, like some antibiotics, can inhibit enzyme function.
Intestinal surgery: Procedures that alter the small intestine's structure can affect enzyme activity.

Prevalence Comparison: Congenital vs. Acquired


Feature	Congenital Sucrase-Isomaltase Deficiency (CSID)	Acquired (Secondary) Sucrase Deficiency
Cause	Genetic mutation in the SI gene.	Damage or inflammation to the small intestine.
Onset	Infancy, typically after introducing sucrose/starch-rich foods.	Can occur at any age, often following an intestinal illness or inflammatory event.
Prevalence	Rare in most populations (e.g., ~1 in 5,000 European descent), much higher in indigenous Arctic groups.	Variable; depends on the prevalence of the underlying condition.
Symptoms	Often severe and persistent, including diarrhea, gas, bloating, and failure to thrive.	Symptoms may be temporary, mild, or moderate, depending on the cause and severity of intestinal damage.
Prognosis	Lifelong condition, though some tolerance may develop with age.	Often temporary, with enzyme function returning after the underlying cause is resolved.

The Role of Genetic Variants

Research suggests that some individuals with heterozygous SI gene mutations (carrying only one copy of a faulty gene) may also experience symptoms of varying severity. This sub-group, often misdiagnosed with IBS, further complicates prevalence statistics and suggests that sucrase deficiency is potentially much more common in symptomatic individuals than previously thought. Studies on patients with IBS have found a notable percentage have an underlying SI deficiency.

Diagnosis and Treatment

Diagnosis of sucrase deficiency typically requires a combination of clinical evaluation and specific tests. This may involve a sucrose hydrogen breath test, a carbon-13 sucrose breath test, or, for definitive diagnosis, a disaccharidase assay from a small intestinal biopsy. Treatment involves two main approaches:

Dietary Management: A sucrose-restricted diet, often managed with the help of a registered dietitian. The level of restriction is tailored to the individual's tolerance.
Enzyme Replacement Therapy (ERT): Medication containing the enzyme sacrosidase, such as Sucraid®, can be taken with meals to help digest sucrose. It is important to note that this therapy does not correct starch maldigestion, and some starch restriction may still be necessary.

Conclusion: The True Commonness of Sucrase Deficiency

While classical, congenital sucrase-isomaltase deficiency is a rare genetic disorder in most populations, the overall prevalence of sucrase deficiency is likely higher than traditionally reported. This is due to the existence of acquired forms, the presence of symptomatic heterozygous carriers, and the persistent issue of misdiagnosis, often leading to it being labeled as IBS. Greater awareness among healthcare professionals and more accessible diagnostic methods are crucial for determining the true commonness of sucrase deficiency and ensuring more individuals receive an accurate diagnosis and effective treatment. For more information, consult reliable health resources like the National Institutes of Health Congenital sucrase-isomaltase deficiency - MedlinePlus.

Frequently Asked Questions

Congenital sucrase deficiency is a genetic disorder caused by mutations in the SI gene and is present from birth, though symptoms appear later. Acquired, or secondary, sucrase deficiency results from damage to the small intestine due to other conditions, such as celiac disease or gastroenteritis.

Yes, sucrase deficiency is frequently misdiagnosed due to symptom overlap with more common gastrointestinal disorders. It is often confused with irritable bowel syndrome (IBS), lactose intolerance, or other types of carbohydrate malabsorption.

Diagnosis can be achieved through several methods, with the gold standard being a disaccharidase assay on a small intestinal biopsy. Other tests include sucrose hydrogen breath tests and carbon-13 sucrose breath tests, which are less invasive but also less definitive.

Treatment involves managing the diet by restricting sucrose and potentially starch intake. Enzyme replacement therapy using a sacrosidase oral solution can also be used to aid in sucrose digestion.

Congenital sucrase deficiency is a lifelong genetic condition, though some individuals may develop a better tolerance for sucrose as they age. Acquired sucrase deficiency is often temporary, with symptoms improving once the underlying intestinal damage has healed.

In individuals of European descent, the classical congenital form is estimated to affect around 1 in 5,000 people. However, studies focusing on symptomatic patients suggest a higher prevalence due to underdiagnosis and milder forms of the condition.

Yes, there is a much higher prevalence of sucrase deficiency among indigenous populations of Greenland, Alaska, and Canada. In these regions, estimates indicate that up to 1 in 20 people may be affected due to a specific genetic founder mutation.