We currently track over 12,000 children and adults with CSID, and we also track approximently 60,000 carriers (parents, siblings, aunts & uncles, cousins and grandparents and other extended family members) who carry the disorder. 

To date there are five phenotypes based on small bowel biopsys for CSID identified and more than 36 mutations of the genotype. This information has been collected directly from medical histories of families who have children with CSID, dieticians, and physicians over the last twenty one years. Most children and some carriers also have a higher incidence of upper respiratory infections, ear, sinus, viral infection, and viral pneumonia.

Additionally, some children and adults (from all phenotype groups) also test positive for additional enzyme disorders. You will also find a summary of all symptoms identified specifically with each phenotype below:

Phenotype A 52% Sucrose (<2grams) and Starch, some are also Lactose Intollerant

This group cannot ingest sucrose or starch without becoming symptomatic, usually  with chronic watery and or acidic diarrhea, abdominal pain, gas.  This group is usually given Sucraid to aid in sucrose digestion of naturally occurring sucrose in fruits and vegetables and an occasional special occasion where sucrose exceeds 2 grams per 100 grams of food. Without Sucraid all sucrose is removed from the diet and children adhere to a diet of less than 2 gram per 100 grams of food.  All starch is eliminated from the diet (not all carbohydrates). Patients in this group must determine the number of grams of naturally occurring sucrose tolerated by the body with one and two mil. dosing of Sucraid depending on body weight and age.  The maximum amount of sucrose that can be tolerated with a dose of Sucraid for this phenotype ranges between 13 and 28 grams per 100 grams of food per meal. This varies quite a bit between children due to specific mutations of the genotype.

Doctors may wish to determine the amount of sucrose consumption possible with a single dose of Sucraid by utilizing the Induction Diet -- by adding increasing amounts of sucrose that naturally occurs in fruits or vegetables every other day until maxium load of sucrose is determined in any given meal and day.  The physician may choose not begin an induction diet with Sucraid or other enzyme supplement, until after the child has reached a normal body weight and has been symptom free for 21 days. Physicians may wish to avoid testing children twice, once at one year, and again at  3-1/2 as children in this group do not seem to improve in starch or sucrose digestion between those periods.   We have not documented any improvement in sucrose or starch digestion at any age for phenotype A. 

Children may have a sucrose load problem in a meal as well as an accumulation during the day. Care must be taken not to remove all carbohydrates from the diet and consultation with a dietician is advised. Children under the age of two usually receive daily vitamin supplementation from formula.  Children over the age of 2 usually require vitamin supplementation in a sucrose and starch free base. We have also documented a statistically significant increase in colon cancer and other bowel disorders in CSID patients, parents, grand parents and extended family members with this mutation who were not diagnosed as a child and did not receive Sucraid to aid in sucrose digestion during childhood or who were diagnosed as an infant or child but continued to eat sucrose and starch in normal amounts without Sucriad or other enzyme replacement.

Phenotype B 7% Sucrose (<2 grams), Limited Starch, some are also Lactose Intollerant

This group cannot ingest sucrose but can ingest limited amounts of  starch without becoming symptomatic, usually with chronic watery and or acidic diarrhea, abdominal pain, gas. This group is usually given Sucraid to aid in sucrose digestion of naturally occurring sucrose in fruits and vegetables and an occasional special occasion. Starch is given in limited amounts.  Patients in this group must determine the number of grams of naturally occurring sucrose tolerated by the body with one and two mil. dosing of Sucraid.  We have very little record keeping of the maximum amount of sucrose that can be tolerated with Sucraid for this group what limited information we do have suggests up to 16 grams per 100 grams of food per meal. This varies quite a bit between children.  Doctors may wish to determine the amount of sucrose and starch consumption possible by the child by adding one gram of starch or sucrose that naturally occurs in grains, fruits or vegetables every other day until max. load in any given meal and day is determined.  One study should be done for starch and another for sucrose tolerance while using Sucraid after the child has reached a normal body weight and has been symptom free for 21 days. Physicians may consider testing children twice once at one year and again at  3-1/2 as children in this group seem to improve in starch digestion between that period.  Contrary to published research the society has not been able to document improvement in starch digestion after 3-1/2 years of age and have not documented any improvement in sucrose digestion at any age for this group of mutations.  Children have a load problem for meals as well as an accumulation during the day. Consultation with a dietician is advised. Children under the age of two usually receive daily vitamin supplementation from formula.  Children over the age of 2 usually require vitamin supplementation in a sucrose and starch free base.

Phenotype C 38% Sucrose (<2 grams), Near Normal Starch, Few are Lactose Intollerant

This group cannot ingest sucrose but can ingest  normal amounts of  starch without becoming symptomatic.  This group seems to have the most severe symptoms, chronic watery and or acidic diarrhea, blood in the stool, vomiting, dehydration.  Small children two and under and infants can loose as much as 20% of their body weight in 4 to 72 hours when sucrose is first introduced to the diet or with accidental ingestion, some have irregular heart rates as well. This group is usually given Sucraid to aid in sucrose digestion of naturally occurring sucrose in fruits and vegetables and an occasional special occasion. Starch is given in normal amounts after the age of three.  Patients in this group must determine the number of grams of naturally occurring sucrose tolerated by the body with one and two mil. dosing of Sucraid.  We have very little record keeping of the maximum amount of sucrose that can be tolerated with Sucraid for this group what limited information we do have suggests between 12 and 40 grams per 100 grams of food per meal. This varies quite a bit between children based on their specific mutation. Doctors may wish to determine the amount of sucrose and starch consumption possible  by the child by adding one gram of starch or sucrose that naturally occurs in grains, fruits or vegetables every other day until max. load in any given meal and day is determined.  One study should be done for starch and another for sucrose tolerance while using Sucraid after the child has reached a normal body weight and has been symptom free for 21 days. Physicians may consider testing children twice once at one year and again at  3-1/2 as children in this group seem to improve to an almost normal level of starch digestion between that period.  Some children in this group consume a normal amount of starch twice a day, the third meal seems to exceed tolerance levels and gas and loose stools occur. We have been able to document a temporary improvement in sucrose digestion between ages 11 and 27, with symptoms reoccurring in mid to late adulthood without Sucraid. We have also documented a statistically significant increase in colon cancer and other bowel disorders in CSID patients, parents, grand parents and extended family members with this mutation who were not diagnosed as a child and did not receive Sucraid to aid in sucrose digestion during childhood or who were diagnosed as an infant or child but continued to eat sucrose and starch in normal amounts without sucriad. Children have a load problem for meals as well as an accumulation during the day. Consultation with a dietician is advised. Children under the age of two usually receive daily vitamin supplementation from formula. Children over the age of 2 usually require vitamin supplementation in a sucrose and starch free base.

Phenotype D 2% Sucrose (<2 grams), Starch and Lactose Intollerant

This group is usually found in Australia and New Zealand and cannot ingest sucrose, lactose or starch without becoming symptomatic, usually with chronic watery and or acidic diarrhea, abdominal pain, gas, swelling, severe red rashes, and bloating. Some children in this group are also diagnosed with ADHD, ADD, learning disorders, restlessness, and anxiety disorders. Diets which work for groups A, B and C do not seem to work for children in this group.  Parents from these countries have contributed to a group D list of foods which most of their children have been able to tolerate. This group is usually given Sucraid to aid in sucrose digestion of less than 1 gram per 100 grams of food containing naturally occurring sucrose in fruits and vegetables and an occasional special occasion. All starch is removed from the diet so ketosis and weight loss can be a problem.  Lactose is removed from the diet unless lactase is utilized by the physician.  Patients in this group must determine the number of grams of naturally occurring sucrose tolerated by the body with one and two mil. dosing of Sucraid.  This varies quite a bit between children.  Doctors may wish to consider adding foods with less than one gram of  naturally occurring sucrose in fruits and vegetables every other day until max. load in any given meal and day is determined before the age of three. Children have a load problem for meals as well as an accumulation during the day. Doctors may also wish to consider the use of lactase for lactose digestion.  Consultation with a dietician is advised. Children under the age of two usually receive daily vitamin supplementation from formula. Children over the age of 2 usually require vitamin supplementation in a sucrose, starch and lactose free base - liquid vitamins may need to be considered where tablets are not available. We have only one family in this group who has multiple family members who have died of colon cancer.

Group E -- Recessive Carriers all Mutations

Siblings, parents, grandparents, some aunts and uncles and 1st cousins of individuals diagnosed with CSID who are heterozygotes have intermediate enzyme values, mild symptoms in infancy, occasional gas, sudden onset of abdominal cramping and pain, and occasional sudden onset of diarrhea in childhood.  In adulthood most siblings and parents and grandparents exhibit no symptoms but 32% suffer from with symptoms ranging from occasional gas and abdominal cramping, to irritable bowel syndrome and colitis. Most parents report that siblings are not big "sweet eaters" and gas usually follows a day when the child has ingested starch in large amounts at all three meals. Of the 32% who have reported symptoms parents and grandparents have reported complete relief of the symptoms usually associated with irritable bowel syndrome and colitis once they reduce their sucrose intake to less than 2 grams of naturally occurring sucrose per 100 grams of food (without Sucraid) and reduce but not eliminate their overall intake of starch. Nearly all who follow the diet for their child's mutation become totally symptom free.

Phenotype F < 1%-- Sucrose (< 1 gram), Starch and some are Lactose Intollerant

This group cannot ingest sucrose or starch without becoming symptomatic, usually with chronic watery and or acidic diarrhea, abdominal pain, gas.  Ths group is extreemly sensitive to sucrose ingestion. This group is usually given Sucraid or other enzyme supplementation to aid in sucrose digestion of naturally occurring sucrose in fruits and vegetables and an occasional special occasion where sucrose exceeds 1 grams per 100 grams of food. Without Sucraid all sucrose is removed from the diet and children adhere to a diet of less than 1 gram per 100 grams of food. All other information is the same as phenotype A.

Summary of Symptoms

Other symptoms this child and or other children in the research literature present with are:

• chronic watery and or acidic diarrhea
• colitis like symptoms 
• upper respiratory infection
• highly susceptible to viral infections
• failure to thrive
• weight loss
• vomiting
• abdominal distension
• irritable bowel syndrome 
• abdominal pain
• bloating
• gassiness
• colic or irritability
• bouts of constipation
• excoriated buttocks
• severe diaper rash or appearance of slight burn from stomach acid
• foul smelling fermented semi solid bowel movements
• dehydration
• malnutrition
• slowed growth 
• slight yellowing of the skin (due to rising carotene levels in the blood)
• inflammation of pyloric sphincter muscle between stomach and superior duodenum/reflux
• possible association with renal calculi (oxalate)
• possible copper malabsorption
• constipation (lack of fiber and dehydration)

Common Misdiagnosis

Allergic gastroenteropathy
toddler's diarrhea
cystic fibrosis
severe gastro-enteritis
colitis
irritable bowl syndrome
diverticulitis
lactose intolerance
glucose-galactose intolerance
fructose intolerance

The following is provided for physicians by QOL Medical: If you are a medical professional and would like a copy of our CSID powerpoint presentation on CD, please e-mail us at: QOL Medical . Congenital Sucrase-isomaltase Deficiency (CSID) is a chronic malabsorption disease characterised by an autosomal recessive inheritable disease of sucrase and isomaltase deficiency (Hauri, 1985; Kerry, 1965; Naim, 1988; Newton, 1996). Patients with CSID have a complete or almost complete lack of endogenous sucrase activity, a marked reduction in isomaltase activity, and a moderate decrease in maltase activity (Auricchio, 1965; Treem, 1993) Sucrase is an enzyme produced in the brush border lining of the small intestine and is responsible for the metabolism of sucrose, a disaccharide commonly known as table sugar, into two component monosaccharides, glucose and fructose, which are then absorbed into the circulation (Sterchi, 1990; Treem, 1995) In the absence of the sucrase enzyme, sucrose cannot be absorbed and passes unchanged into the large intestine. The presence of intact disaccharides in the intestinal lumen leads to osmotic retention of water, resulting in loose stools (Treem, 1995). Unabsorbed sucrose in the large intestine is broken down by colonic bacteria, producing among other things the gases Hydrogen, methane, and carbon dioxide. These gases generate gastrointestinal discomfort including excessive gas, bloating, abdominal pain and cramps, watery diarrhea, nausea and vomiting (Berkow, 1992; Davidson, 1967) Thus, children born with CSID develop a malabsorption syndrome upon first exposure to sucrose in their diet. Usually this is in the form of infant formula since breast milk does not contain sucrose. Because these children are unable to digest a significant portion of their caloric intake, they often have retarded growth and a failure to thrive (Antonowicz, 1972; Gudman-Hoyer, 1985; Newton, 1996; Treem, 1995). Added features may include irritability, lethargy and sleep disturbances. CSID is a difficult disease to diagnose. Studies have shown that in pediatric patients with chronic diarrhea of unknown origin 4-10% had CSID (Davidson, 1983; Larcher, 1977). The rationale for SUCRAID is very straightforward - replacement of the missing endogenous sucrase with an exogenous sucrase that retains enzymatic activity when given orally. It should be noted that although SUCRAID provides replacement therapy for the deficient sucrase enzyme, it does not provide specific replacement therapy for isomaltase deficiency (Treem 1996). Therefore, it may be necessary to continue a restriction in the starch content of the diet in order for patients to optimize diminishment of disease symptoms(Greene, 1972)

The molecular basis of CSID is still not elucidated. However, it has been proposed that different molecular defects or mutations in the SI gene are responsible for CSID. This hypothesis has been strongly supported by the analysis of several cases of CSID, which has led to the identification of five different phenotypes of SI. Phenotypes I and II, for instance, are characterized by an intracellular accumulation of mannose-rich SI in the ER and the Golgi, respectively. In phenotype III an enzymatically inactive, but transport-competent, SI is expressed. Phenotype IV expresses a partially folded, mannose-rich SI molecule that is missorted to the basolateral membrane. Finally, phenotype V reveals an SI species that undergoes intracellular degradation leaving behind the isomaltase subunit that is correctly targeted to the brush border membrane This genetic variability may account for the range in the severity of symptoms encountered by patients affected by the disease

The prevalence of CSID is not known with certainty due to the phenotypic variations described in the previous slides. Studies have tried to account for the number of heterozygote carriers in the general population based on measurements of sucrase activity in small bowel biopsy specimens. Peterson and Herber reported an 8.9% frequency of heterozygotic individuals in a sampling of the general US population. Welsh et al found only a 2% incidence of heterozygotic individuals in a more specific caucasian population. The absence of sucrase activity in patients as young as four months of age and symptoms in patients with CSID appearing as soon as sucrose is introduced to the diet, support the idea that this deficiency is present at birth. Up to 10% of the Greenland eskimo population was found to be homozygotes and consequently affected by the disease. The high prevalence in some populations could be the result of biological mutations produced by those who do not traditionally ingest sucrose containing foods. Isolated from a western style diet, this has not been a clinical problem, but the migration of western dietary culture now means that CSID symptoms may be experience by these populations. Although rare in the US, 1 in a 1000 patients have some degree of SI deficiency and the similarity of S-I deficiency symptoms to those of other conditions and diseases makes it conceivable that it is misdiagnosed or under- diagnosed both in children and adults as conditions such as toddler's diarrhea or Irritable Bowel Syndrome.

© CSIDINFO.Com, CSID Society (1994-2016)