Managing CSID in Pediatric Patients

Managing pediatric patients with Congenital Sucrase-Isomaltase Deficiency (CSID) requires attention to concerns unique to their age. Congenital Sucrase-Isomaltase Deficiency can be particularly devastating for infants and small children, as it may result in severe nutritional malabsorption. Malabsorption and fermentation of digested carbohydrates can also lead to accelerated motility and broad malabsorption of all dietary nutrients. This, in turn, can lead to a failure to thrive during a critical developmental window when significant growth and development typically occur. Malnutrition and severe diarrhea can also lead to dehydration, metabolic acidosis, hypercalcemia, and developmental delay.1

There are Several Important Indicators to Monitor in Pediatric Patients

  • Age of onset and dietary changes. Congenital Sucrase-Isomaltase Deficiency often presents when infants are first weaned from breast milk and begin consuming fruit, baby food, juice, and medications containing sucrose. Take a detailed history of what and when different foods and beverages were first introduced to investigate potential associations with the onset of symptoms.
  • Shape and frequency of bowel movements. Children with CSID may have osmotic diarrhea, mild steatorrhea, or chronic diarrhea and may also vomit after consuming sucrose.1 Chronic diarrhea is defined as passing loose, watery stools three or more times a day for at least four weeks. Diarrhea from carbohydrate malabsorption is usually acidic and can lead to severe diaper rash and excoriated buttocks. The Bristol stool chart is a helpful schematic which allows parents to discuss and accurately characterize the shape and consistency of their children’s bowel movements. There may be reports of explosive diarrhea and a foul stool odor due to the malabsorption and fermentation of ingested carbohydrates.
    • Parents are often surprised to learn that the frequency of bowel movements in normal, healthy children can vary quite a bit; for example, it is higher in breastfed infants. Normal stool colors include yellow, green, or brown and can change with age. Stool consistency varies with diet. Stools tend to be softer in breastfed babies or older children eating a high-fiber diet.
Table 1. Frequency of Defecation in Normal, Healthy Children*
Age Minimal Maximal
Infant breastfed 1 per 10-14 days 10 per day
Infant/toddler to 3 years 1 per 2 days 3-4 per day
Older children 3 per week 3 per day

*Adapted from Auth 2016, Pediatrics and Child Health.2

  • Biometrics. Track height, weight, and head circumference relative to age in order to spot trends that might indicate a failure to thrive or an improvement from dietary intervention and/or sucrase enzyme replacement therapy following a CSID diagnosis. The World Health Organization growth charts are recommended for assessing the relative development of American children 0 to 2 years old.3 For patients 2 to 20 years old, refer to the Centers for Disease Control and Prevention clinical growth charts.4
  • Dehydration. Pediatric patients with CSID are at a high risk of becoming dangerously dehydrated, caused by large losses of body water through chronic diarrhea and vomiting. However, reports by parents about diarrhea, vomiting, or decreased oral intake are not sufficient to identify dehydration. Instead, a physical examination that includes determining capillary refill time (CRT) is a more objective measure of potential dehydration. A CRT of more than two seconds is a red flag that merits further investigation.5,6 In infants, CRT is measured on the sternum; in older children, it is measured from a finger or arm held at heart level.5 Other signs of dehydration include abnormal skin turgor, the absence of tears, dry mucous membranes, general ill appearance, sunken eyes, and an abnormal respiratory pattern. Skin turgor can be assessed by pinching the skin on the lateral abdominal wall, level with the umbilicus.5 Heart rate and respiratory rate can be compared to age-specific normative values to identify any abnormalities.
  • Family history. Congenital Sucrase-Isomaltase Deficiency was initially thought to be a homozygous recessive disorder; however, CSID symptoms can occur in individuals who are carriers of compound heterozygous or heterozygous variants.1 If a pediatric patient has CSID, siblings and one or both parents may also benefit from CSID screening and interventions.
  • Sufficient calories. After a diagnosis of CSID, young children or parents may severely restrict dietary carbohydrate intake in order to manage gastrointestinal symptoms. Dietary guidance may be required to encourage a diet that is tolerated and promotes growth. One intervention would be an initial short period of eliminating all dietary carbohydrates, followed by systematic and gradual reintroduction of carbohydrates, based on foods and amounts that do not generate gastrointestinal symptoms. Enzyme supplementation can help alleviate symptoms and provide the ability to increase sucrose consumption and total calories. Extreme dietary restriction of all carbohydrates should be avoided in growing children, as it may result in periodic hypoglycemia.



  1. Cohen SA. The clinical consequences of sucrase-isomaltase deficiency. Mol Cell Pediatr. 2016;3(1):5. doi:10.1186/s40348-015-0028-0
  2. Auth MK, Vora R, Kokai G. Investigation of chronic diarrhea. Paediatr Child Health (Oxford). 2016;26(10):423-32. doi:10.1097/00005176-198506000-00010
  3. Grummer-Strawn LM, Reinold C, Krebs NF; Centers for Disease Control and Prevention. Use of the World Health Organization and CDC growth charts for children aged 0-59 months in the United States. MMWR Recomm Rep. 2010;59(RR-9);1-15.
  4. Centers for Disease Control and Prevention. CDC Growth Charts. Last updated December 15, 2022.
  5. Fleming S, Gill P, Jones C, et al. The diagnostic value of capillary refill time for detecting serious illness in children: a systematic review and meta-analysis. PLoS One. 2015;10(9):e0138155. doi:10.1371/journal.pone.0138155
  6. Canavan A, Arant BS Jr. Diagnosis and management of dehydration in children. Am Fam Physician. 2009;80(7):692-696.