OVERVIEW
Fructose intolerance (FI), also known as fructose-1,6-bisphosphate aldolase-deficiency disease, is a congenital disorder in which the enzyme is deficient or has reduced activity due to a mutation in the B gene for fructose-1-phosphate aldolase, resulting in hypoglycemia and impairment of hepatic and renal function with manifestations of hepatomegaly, jaundice, and renal tubular acidosis. It is a rare congenital disease with an uncertain incidence of about 1/20000.
Etiology
The disease is an autosomal recessive disorder. It is caused by a mutation in the aldolase B gene, which alters the structure and activity of aldolase B. The accumulation of fructose 1-phosphate in the liver leads to the inhibition of some other enzymes in the liver, including phosphorylase, fructose 1,6-bisphosphatase, hepatic aldolase, and fructokinase, and as a result, the hepatic glycogenolysis and gluconeogenesis are impaired, leading to hypoglycemia. fructose 1-phosphate builds up in the liver, kidneys, and intestines, causing chronic damage. The accumulation of fructose 1-phosphate in the liver, kidney, and intestine causes chronic damage.
Symptoms
Patients with hereditary fructose intolerance have no clinical symptoms until they have absorbed fructose or sucrose, usually from fruits, fruit juices, or sweetened cereals. If a newborn is given food or formula containing these sugars after birth, the child will quickly develop symptoms. Early clinical signs are similar to those of galactosemia and include jaundice, hepatomegaly, vomiting, depression, irritability, and convulsions. Acute fructose ingestion results in hypoglycemia; prolonged fructose ingestion results in growth retardation and liver lesions. If fructose intake continues and hypoglycemic symptoms recur, children develop loss of appetite, diarrhea, weight loss, hepatomegaly, jaundice, edema, and ascites, and liver and kidney failure progresses, ultimately resulting in death. Children or adult patients, on the other hand, soon after eating sucrose, severe abdominal pain, nausea and vomiting, mostly without hypoglycemia, for a long time, most of the automatic refusal of sweets.
Examination
1. Urine examination: fructose can be detected, which can be distinguished from glucose by chromatography.
2. Blood biochemistry examination: during the acute attack of hypoglycemia, blood inorganic phosphorus, uric acid, lactic acid, pyruvic acid, free fatty acid and glycerol are elevated. Chronic patients have liver function damage, showing elevated serum aminotransferases and prolonged blood coagulation time. Renal function may be abnormal.
3. Fructose tolerance test: blood glucose and/or blood phosphorus are lower than normal.
4. Ultrasound: chronic patients have fatty infiltration and fibrosis in the liver, but there is no specificity.
5. Liver biopsy: shows fatty infiltration, fibrous tissue hyperplasia and liver mitochondria with obvious abnormalities.
Diagnosis
According to the history and clinical manifestations, children with nausea, vomiting and hypoglycemia after feeding fructose-containing food; or with unexplained hypoglycemia and hepatomegaly should be considered as possible cases of this disease. Liver biopsy or intestinal mucosal biopsy to determine aldolase B activity may be used to assist in the diagnosis of this disease.
Treatment
Avoid intake of food containing fructose, sucrose and sorbitol; when acute hypoglycemia occurs, supplement glucose in time to correct it; in addition to dietary treatment for those with liver and kidney function damage, active treatment should be taken to protect the liver and kidneys, and avoid the use of drugs that damage the liver and kidneys.