For Patients – F.A.Q.

What is Congenital Sucrase-Isomaltase Deficiency (CSID)?

CSID is an inherited error of metabolism in which patients are born with absent or low levels of two digestive enzymes: sucrase and isomaltase.21 Sucrase is the intestinal enzyme that aids in the breakdown of sucrose (simple table sugar) into glucose and fructose, which are used by the body as fuel. Isomaltase is one of several enzymes that helps digest starches.

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What are the symptoms of CSID?

Symptoms of CSID can be varied. Chronic, watery diarrhea with or without failure to thrive, and recurrent, unexplained abdominal pain are common symptoms in infants and toddlers. Patients may also present with abdominal distention (swelling), gassiness, colic, irritability, excoriated buttocks, diaper rash, and vomiting.3 A minority of patients may require hospitalization due to dehydration, malnutrition, muscle wasting, and weakness.9

In older children and adults, a prolonged period of missed diagnosis may occur with the patient “learning to live with” their uncomfortable gastrointestinal symptoms, or assuming their ongoing gastrointestinal problems to be “normal”. Recurrent symptoms similar to those caused by CSID, such as frequent bowel movements, chronic diarrhea, unexplained abdominal pain, gassiness, bloating, weight loss, abdominal distention, and vomiting should not be ignored. These can all be symptoms of some form of carbohydrate malabsorption, including CSID. Consultation with a gastroenterologist is recommended to discuss any recurring, persistent gastric symptoms.

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How is CSID diagnosed?

After referral to a gastroenterology clinic, the physician will perform routine analysis of patient well-being, physical examination, clinical history, family history, and diet history. Based on this information, the physician may order tests to determine the exact diagnosis. Often with rare diseases, there is a process of discovery which sometimes requires a systematic process of elimination of other more common ailments. If CSID is suspected, the diagnostic workup should include an upper endoscopy in which several biopsies (tissue specimens) will be obtained from the small intestine and sent for a specialized laboratory analysis of enzymatic activity.

Some physicians may choose to initiate a brief therapeutic trial with Sucraid® (sacrosidase) Oral Solution, a safe and effective oral enzyme replacement therapy for sucrase deficiency, to observe whether the patient responds clinically to treatment.1

Depending on the age of the patient, a treating physician may order a hydrogen breath test. An increase in breath hydrogen output suggests that enzymatic function is not working properly. Currently there are no approved genetic tests available for CSID.

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What are some common misdiagnoses?

The diagnosis of CSID can be missed, especially if patients have mild, nonspecific symptoms that resemble other more common gastrointestinal diseases. Common misdiagnoses may include toddler’s diarrhea, diarrhea predominant irritable bowel syndrome (IBS), or recurrent abdominal pain predominant IBS. In most cases of CSID, correct diagnosis is delayed while other more common causes of severe, chronic diarrhea are considered.10 Patients may be diagnosed with food allergy or intolerance to cow's milk (lactose intolerance) or soy protein. Once infancy is passed and a larger variety of foods are added to the diet, it is more difficult to correctly identify sucrose malabsorption as the primary cause of symptoms. Allergic gastroenteropathy, cystic fibrosis, celiac disease, severe viral gastroenteritis, lactose intolerance, glucose-galactose intolerance or other causes of intractable diarrhea are often considered in diagnosis, as all of these diagnoses may cause similar symptoms to CSID.

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I’ve been diagnosed/my child has been diagnosed with CSID. Now what?

Being diagnosed with CSID may present an immediate, overwhelming feeling but it is important to understand CSID is not a fatal disorder. The symptoms of CSID often have a substantial impact on both the patient’s and caregiver's life, but with consistent compliance to dietary management, life can return to a sense of normalcy. Working with a gastroenterologist and a registered dietician/nutritionist will assist the patient/caregiver in understanding the importance of dietary management.

CSID patients have also shown marked improvement with regular Sucraid® therapy, which may allow the consumption of a normal sucrose-containing diet.13 Compliance with Sucraid® treatment is generally easier to achieve than with dietary management alone. Overall, 86% of CSID patients aged ≤3 years and 77% of patients aged >3 years became asymptomatic while on therapy with Sucraid® Oral Solution.13 Sucraid® is the only approved enzyme replacement therapy for the treatment of genetically determined congenital sucrase deficiency.

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What causes CSID and will my child outgrow CSID?

CSID is a rare, inherited disorder that is not outgrown. Congenital means it was “present at birth” and the deficiency is not acquired due to infection or other external influence. Both parents must carry the recessive gene for a child to be born with the disease.

All CSID patients lack sucrase activity, but the degree of isomaltase activity varies, suggesting the disease is not a consequence of a complete lack of SI gene expression. Therefore, CSID is considered a heterogenous condition with variability of severity between patients.

Since proper sucrose digestion requires production of new sucrase-isomaltase enzymes each time food is consumed and CSID patients lack the ability to produce sucrase-isomaltase, CSID is chronic and cannot be outgrown.

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How does CSID differ from lactose intolerance?

The table below summarizes how CSID is different from lactose intolerance, another more common carbohydrate malabsorption condition.

Lactose Intolerance CSID
  • Lactose intolerance is the intestine’s inability to metabolize lactose due to a lack of the enzyme lactase.
  • Lactose is a type of carbohydrate found in milk and other dairy products.
  • If the body does not produce enough lactase, then a deficiency is identified and symptoms occur.
  • Ingestion of milk sugars causes symptoms similar to those in CSID.
  • Lactose intolerance is not caused by a genetic mutation and is very common.
  • Onset can occur at any age.
  • CSID is caused by a mutation of a gene in chromosome 3 producing a lack of the sucrase enzymatic activity, making the body unable to digest sucrose.
  • Sucrose is commonly referred to as table sugar, and is naturally found in all fruits and vegetables, and is a common additive to many processed foods.
  • CSID is considered very rare.
  • CSID is congenital, or present at birth.

Table 1. Comparison of CSID and lactose intolerance

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What does Sucraid® do?

CSID is the result of the absence of sucrase, the enzyme that plays a role in the body’s breakdown of sugar. Enzyme replacement therapy with Sucraid® acts as a substitute for the missing enzyme, and can reduce or eliminate the symptoms of this disease when taken as directed.1

Although Sucraid® provides replacement therapy for deficient sucrase, it does not provide specific replacement therapy for deficient isomaltase.1 Therefore, restricting starch in the diet may still be necessary to help reduce gastrointestinal symptoms as much as possible. The need for dietary starch restriction for patients using Sucraid® should be evaluated under a physician’s care.

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How do I take Sucraid®?

The recommended dosing of Sucraid® is as follows.

Table 2. Recommended dosing of Sucraid®

    The following should be noted in regards to delivery, storage and expiration of Sucraid®: 

  • It is suggested that half of each dose be taken before the meal and the other half be taken during the meal. The divided dose is important as the first half of the dose is used to decoy pepsin which is in the stomach and could otherwise reduce Sucraid’s effectiveness.
  • Sucraid® should not be dissolved in or taken with fruit juice, since its acidity may reduce enzyme activity.
  • The delivery beverage should be served cold or at room temperature and should never be warmed or heated as this may decrease the potency of the enzyme.
  • Sucraid® should be stored in the refrigerator at 36ºF-46ºF (2°C-8°C) and should be protected from heat and light.
  • Always throw away the bottle, along with any remaining Sucraid®, four weeks after first opening it due to the potential for bacterial growth.

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What are the side effects of Sucraid®?

No common side effects exist with Sucraid® and no reports of overdose have occurred. Patients with a known sensitivity or allergy to yeast, yeast products, glycerin (glycerol), or papain should not use Sucraid®.

Only four patients in the registration clinical trial experienced adverse events, including wheezing, vomiting, pallor, and dehydration.14 Three patients completed the trial and continued in a long-term, open-label trial of sacrosidase. The fourth, who was hospitalized for wheezing, withdrew from the trial. The majority of the adverse events were attributed to concurrent illnesses common in childhood.

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What changes should be made to my/my child’s diet?

It is important once a diagnosis of CSID has been made that the patient/caregiver work with a qualified nutritionist to review dietary restrictions, and develop an understanding of food labels and ingredients (including alternative food and additive names).

Although Sucraid® provides replacement therapy for deficient sucrase, it does not provide specific replacement therapy for any deficient isomaltase.1 Therefore, restricting starch in the diet may still be necessary to reduce symptoms as much as possible. The need for dietary starch restriction for patients using Sucraid® should be evaluated under a physician’s care.
Patient dietary management, as well as disease and therapeutic education are the best tools to keep the potential for adverse incidences to a minimum.
The use of Sucraid® will enable the products of sucrose hydrolysis—glucose and fructose—to be absorbed.1 This fact must be carefully considered in planning the diet of diabetic CSID patients using Sucraid®.

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How do I access Sucraid®?

How to Order Sucraid®

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Glossary of Terms Associated with CSID

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Patient Prescribing Information

Full Prescribing Information (pdf)

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Other Patient Resources

  1. CLIMB- Children Living with Inherited Metabolic Diseases (UK)
  2. NORD- National Organization for Rare Disorders (USA)
  3. March of Dimes
  4. Madison's Foundation
  5. GARD (ORD/NIH) National Institutes of Health, Office of Rare Diseases, Genetic and Rare Diseases Information
  6. Parent Support- Share Your Story

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Important Safety Information

For a complete discussion of indications, usage, contraindications, warnings, precautions, adverse reactions, and overdosage, please see full prescribing information attached. Do not use Sucraid® with patients known to be hypersensitive to yeast, yeast products, or glycerin (glycerol). Sucraid may contain papain which can cause allergic reactions in some patients. Adverse experiences with Sucraid in clinical trials were generally minor and were frequently associated with underlying disease. In clinical studies of up to 54 months duration, physicians treated a total of 52 patients with Sucraid. The adverse experiences and respective number of patients reporting each event were as follows: abdominal pain(4), vomiting(3), nausea(2), diarrhea(2), constipation(2), insomnia(1), headache(1), nervousness(1), and dehydration(1). Note: diarrhea and abdominal pain can be a part of the clinical presentation of the genetically determined sucrase deficiency, which is part of congenital sucrase-isomaltase deficiency. The effects of Sucraid have not been evaluated in patients with secondary (acquired) disaccharidase deficiency. In one clinical trial, one patient, a four year old boy who was being treated for asthma, experienced severe wheezing necessitating admission into the ICU. While reported reactions are extremely rare, care should be taken when administering initial doses of Sucraid to observe any signs of acute hypersensitivity reaction. Care should be taken to administer initial doses of Sucraid near a facility where acute hypersensitivity reactions can be adequately treated.1