Understanding Maltose Deficiency
Maltose, or malt sugar, is a disaccharide made of two glucose units. It is a component of many starches and grains. To be absorbed by the body, maltose must first be broken down by the enzyme maltase, which is typically found alongside sucrase in the small intestine brush border. Therefore, a specific deficiency of just maltase is exceptionally rare. Instead, maltose malabsorption is most commonly a symptom of a broader condition, Congenital Sucrase-Isomaltase Deficiency (CSID), which is an inherited metabolic disorder affecting the enzyme complex responsible for breaking down both sucrose and maltose.
When the enzyme is deficient, the undigested maltose passes into the large intestine, where it attracts water and is fermented by gut bacteria. This fermentation process is the root cause of the gastrointestinal symptoms associated with the condition. While the congenital form is lifelong, some individuals may experience a milder, acquired form of sucrase-isomaltase deficiency due to damage to the small intestinal lining from other illnesses.
Key Gastrointestinal Symptoms
The symptoms of maltose malabsorption are predominantly gastrointestinal and often appear after consuming foods containing maltose or starch. The severity can vary from person to person and is typically related to the amount of sugar ingested.
Common signs include:
- Diarrhea: The undigested maltose in the large intestine creates an osmotic effect, pulling water into the colon and leading to watery, sometimes explosive, diarrhea.
- Abdominal Pain and Cramping: The fermentation of unabsorbed sugars by bacteria produces gas, causing painful stomach cramps and discomfort.
- Bloating and Distension: Excess gas production from bacterial fermentation leads to a swollen, bloated feeling and visible abdominal distension.
- Excessive Gas (Flatulence): A direct result of the fermentation process in the colon is a noticeable increase in gas production.
- Nausea and Vomiting: Some individuals, especially infants and children, may experience nausea and occasional vomiting.
- Failure to Thrive and Poor Weight Gain: In infants and young children, chronic diarrhea and poor nutrient absorption can prevent proper growth and weight gain.
- Malnutrition: Over time, the inability to properly absorb carbohydrates can lead to general malnutrition and vitamin deficiencies.
Symptom Presentation by Age
Infants and Young Children: Symptoms typically appear when infants are weaned from breast milk or lactose-only formula and begin consuming fruit juices, cereals, and other starchy foods. The presentation is often severe, with chronic diarrhea and failure to thrive being prominent signs.
Older Children and Adults: The presentation can be less dramatic and more varied. Some individuals may develop a tolerance to starches as they get older, but remain sensitive to sucrose. Adults may experience symptoms that closely resemble irritable bowel syndrome (IBS) or other non-specific digestive issues. The intermittent nature of the symptoms, which often correspond to dietary intake, can make diagnosis challenging.
Diagnosis of Maltose Deficiency
Since maltose deficiency is typically part of CSID, the diagnosis process focuses on confirming the sucrase-isomaltase deficiency.
Comparison of Diagnostic Methods
| Diagnostic Method | How It Works | Pros | Cons |
|---|---|---|---|
| Disaccharidase Assay (Biopsy) | Measures enzyme activity from small intestinal tissue samples. | Gold standard; most accurate and reliable. | Invasive procedure (endoscopy); technically challenging. |
| Sucrose Hydrogen Breath Test | Measures expired hydrogen gas after consuming a sucrose solution. | Non-invasive and can be useful for screening. | Less accurate than biopsy; false positives/negatives can occur. |
| Therapeutic Trial | A strict, low-maltose, low-sucrose diet is followed to observe symptom improvement. | Clinically meaningful and low-risk. | Not specific to CSID; symptoms can be masked by diet. |
| Genetic Testing | Analyzes the SI gene for mutations that cause CSID. | Confirmatory and specific. | Can be expensive and may not cover all possible mutations. |
Management and Treatment
There is no cure for congenital sucrase-isomaltase deficiency, but symptoms related to maltose deficiency can be effectively managed. The primary treatment involves dietary modifications to restrict the intake of carbohydrates that are not properly digested. This typically means limiting sources of sucrose and, depending on individual tolerance, starch.
- Dietary Adjustments: Individuals may need to avoid or severely limit foods high in maltose and starch, such as grains, bread, pasta, and some processed foods. For infants, a change to a maltose- and sucrose-free formula is necessary.
- Enzyme Replacement Therapy (Sacrosidase): For managing sucrose malabsorption, a prescribed enzyme replacement called sacrosidase (Sucraid®) can be effective. However, it is important to note that this enzyme specifically helps with sucrose digestion and does not aid in the digestion of maltose or starch.
Conclusion
Maltose deficiency, almost always a component of congenital sucrase-isomaltase deficiency (CSID), is a metabolic disorder characterized by the body's inability to properly digest maltose and starch. The undigested sugars trigger a range of gastrointestinal symptoms including chronic diarrhea, bloating, and abdominal pain. In infants, this can manifest as failure to thrive, while in adults, it may mimic IBS. Diagnosis is confirmed through a small intestinal biopsy, though other less invasive methods are available. Management focuses on dietary restrictions of sucrose and starch, with enzyme replacement therapy used to specifically address sucrose intolerance. With proper management, individuals can lead normal lives by controlling their symptoms through diet and supplementation. iffgd.org provides further information and support for those with CSID.
