Hereditary fructose intolerance

Introduction There are three obstacles to the fructose metabolic pathway caused by autosomal recessive inheritance: 1. Fructose kinase deficiency (or essential fructoseuria, essential fructosuria) is caused by the lack of fructokinase in the liver, so that fructose can not be phosphorylated and can not be further metabolized in the liver, so the concentration of fructose in the blood of patients is ingesting Fructose is obviously elevated and excreted from the urine. There is no obvious clinical symptoms in this disease. The significance of correct diagnosis is to prevent misdiagnosis of diabetes and add treatment. 2. Hereditary fructose intolerance is caused by the deficiency of fructaldolase (fructalose-, 6-diphosphatealdolase). 3. Fructose-1,6-bisphosphatase deficiency, which is a catalytic enzyme in the glucose metabolism pathway, but is customarily summarized in the defect of fructose metabolism.

Cause

The cause of hereditary fructose intolerance:

The disease belongs to autosomal recessive genetic disease. The 14g-labeled fructose is used to examine the patient's liver fructose-1-phosphate aldolase, which is found to be a normal 0-12%, showing a significant decrease.

an examination

Related inspection

Pancreatic exocrine function test blood glucose

Examination of the diagnosis of hereditary fructose intolerance:

Clinical manifestations: age of onset is related to the dietary composition used. Because most of the milk contains sucrose, newborns who are given artificial feeding after birth often have vomiting, diarrhea, dehydration, shock and bleeding tendency within 2 to 3 days. Symptoms of liver failure; breast-fed infants are given sucrose or fructose-containing food supplements in the infant period. Within 30 minutes of feeding, vomiting and abdominal pain, cold sweating, and symptoms of hypoglycemia such as coma and convulsions occur. The child quickly developed loss of appetite, diarrhea, weight loss, liver, jaundice, edema and ascites. Some children automatically refuse to eat during infancy due to repeated symptoms of sweet food. This protective behavior allows the child to grow healthy until adulthood. A small number of children may die from progressive liver failure due to undiagnosed treatment.

Complications: vomiting, diarrhea can cause dehydration shock, acute liver failure, cirrhosis, jaundice, edema, ascites, bleeding, coma, etc., or hypoglycemia, convulsions and other symptoms, weight does not increase liver and so on.

Diagnosis: The diagnosis can be based on: 1. Clinical characteristics After removing fructose from food, the clinical symptoms disappear within a few hours. 2. Fructose tolerance test (fructosetolerancetest) showed that blood glucose and blood phosphorus decreased rapidly while fructose fatty acid and lactic acid increased, but this test is easy to cause hypoglycemia, so it should be used with caution, and the amount of fructose used should be reduced, oral administration of 0.5g / kg intravenous Children who are halved can also be orally administered at 3g/m2. 3. Bioassay Determination of enzymes in the liver and intestinal mucosa showed a significant decrease in enzyme activity.

Hereditary fructose intolerance laboratory test:

1. Blood biochemical examination: In the presence of acute symptoms, children should present hypoglycemia and blood phosphorus, potassium and potassium are transiently reduced serum fructose, lactic acid, pyruvic acid and uric acid. In hypoglycemia, serum insulin was decreased and glucagon adrenaline and growth hormone concentrations were increased. Plasma free fatty acids increased significantly with these hormones, which was different from normal people. Fructose-1,6-bisphosphatase deficiency (autosomal recessive inheritance, its clinical manifestation is similar to fructose intolerance mainly liver enlargement) can cause hypoglycemia after eating fructose and when starving The original cumulative disease "ketohypoglycemia" and the disease are confused. The detection of serum bilirubin, transaminase and coagulation factors contributes to the diagnosis and treatment of acute liver failure.

2. Urine biochemical examination: urine fructose should be detected in children with suspected acute illness. Children who continue to eat fructose often have renal tubular acidosis and Fanconi syndrome-like tubular reabsorption. Therefore, urine pH protein amino acids and bicarbonate should be tested.

3. Fructose tolerance test: Determination of fructose, glucose, uric acid and aminotransferase in blood can be diagnosed after intravenous injection of fructose 200-250mg/kg. This test should be performed several weeks after the condition is stable.

4. Enzymatic examination: liver, kidney or intestinal mucosal biopsy can be used, but not necessary for diagnosis.

Differential diagnosis

Identification of the symptoms of hereditary fructose intolerance and confusion:

1. Primary glucose malabsorption: In the primary glucose malabsorption, congenital lactase deficiency, sucrose-isomaltase deficiency, and glucose-galactose malabsorption are autosomal recessive genetic diseases, which are rare in clinic. In addition to the sucrose-isomaltase deficiency can be added to the diet after the onset of sucrose, the rest of the disease soon after birth. The histology of small intestinal mucosa biopsy was normal, and the corresponding disaccharidase activity was reduced. Glucose-galactose malabsorption and disaccharidase activity were normal. Malabsorption is caused by the congenital deficiency of Na-glucose and Na-galactose carrier protein, and the fructose absorption of the sick child is good.

There are two other types of primary lactase deficiency, which are all physiologically deficient: 1 developmental lactase deficiency, lactase activity at 30 weeks of fetus is only 30% of full-term children, and gradually increases to It is only fully developed during full-term delivery, so lactase activity in premature infants is low and lactose intolerance is prone to occur. 2 Lack of late lactase, in general, lactation of the small intestine epithelial brush border lactase activity is sufficient. After 3 to 5 years of age, it gradually declines, and some children may cause lactase deficiency or lactose intolerance. The incidence rate varies among different ethnic groups. The incidence rate in the western and northern European population is about 10%, and the incidence rate in the oriental population is higher. In China, 225 children aged 5-7 years old were tested. As a result, lactose malabsorption accounted for 71.6%, and lactose intolerance accounted for 20.5%.

2. Secondary lactase deficiency and monosaccharide malabsorption: clinically more common, because lactase is distributed at the top of the small intestine villi, all diseases that can cause damage to the intestinal mucosal epithelial cells and their brush borders can be secondary to disaccharide Lack of enzymes, severe and extensive lesions, can also affect the absorption of monosaccharides, such as acute enteritis (especially involving the upper part of the small intestine, such as rotavirus enteritis, blue giardia infection, etc.), chronic diarrhea, protein-heat card malnutrition , immunodeficiency disease, celiac disease and small bowel surgery injuries.

In the upper part of the jejunum, lactase is mainly found in the brush border of the epithelial cells at the top of the villus. The invertase is abundant in the villus, while the maltase is widely distributed in the intestine and is the most abundant. Therefore, lactose occurs when the small intestine is damaged. The enzyme is the most susceptible, and the recovery is the slowest, the most common clinical; maltase is the least susceptible, and the invertase is rare and rare, and only when the intestinal mucosa is seriously damaged, the activity is decreased. At this time, the lactase activity has been affected, and Often accompanied by a single sugar absorption disorder.

3. Fat malabsorption: Fat malabsorption, also known as steatorrhea, is a syndrome caused by fat digestion and malabsorption, which can be seen in many diseases such as pancreas, liver, gallbladder and intestinal diseases. The dysentery caused by intestinal lesions is accompanied by malabsorption of other nutrients, which is called malabsorption syndrome.

4. Protein malabsorption: protein alone is poorly absorbed, clinically rare, generally occurs when the intestinal mucosa is extensively damaged, often accompanied by fat malabsorption. Malabsorption syndrome is sometimes associated with poor protein absorption. Loss of intestinal mucosal exudation, such as milk or soy protein tolerance, celiac disease, blue giardiasis, inflammatory bowel disease and intestinal lymphatic dilatation can occur in the intestinal tract, which can be determined by measuring feces. The 1 antitrypsin confirmed that this protein is present in the plasma and cannot be digested and hydrolyzed in the intestinal tract, so when the intestinal mucosa has protein exudation, 1 antitrypsin can be detected in the feces.

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