Galactosemia
Introduction
Introduction to galactosemia Galactose-1-phosphateuridyltransferase (Gal-1-PUT) is a congenital metabolic disorder caused by galactose-1-phosphateuridyltransferase (Gal-1-PUT) deficiency. Typically, the disease occurs during the perinatal period, and vomiting, refusal to eat, weight loss, and lethargy often occur several days after feeding the milk, followed by jaundice and liver enlargement. If you can not continue to feed the milk in time, it will lead to further deterioration of the disease, and end-stage symptoms such as ascites, liver failure, and hemorrhage occur within 2 to 5 weeks. basic knowledge The proportion of illness: 0.001% Susceptible people: good for young men and women Mode of infection: non-infectious Complications: jaundice ascites
Cause
Cause of galactosemia
(1) Causes of the disease
Classical galactosemia occurs in the second step of galactose metabolism, in which 1-phospho-galactosidase is deficient, resulting in an autosome that is caused by the accumulation of its precursor 1-phosphate-galactose. Recessive genetic diseases, liver, kidney, crystal and brain tissue are the main affected organs.
(two) pathogenesis
The metabolism of galactose is mainly carried out in the liver.
Defects in any of the enzymes required for galactose metabolism can lead to metabolic disorders of galactose, which directly cause an increase in the concentration of galactose and galactose-1-phosphate in the blood, of which galactose-1- Galactosemia caused by a deficiency in uridine transferase (GALT) is most common.
The galactose-1-phosphate uridine transferase deficiency is caused by gene mutation and is autosomal recessive. The gene of galactose-1-phosphate uridine transferase is located in the short arm p13 region of chromosome 9, in the population. The gene frequency is 1/150, the patients are homozygous, the heterozygotes are generally not affected, the parents of the patient may be homozygous or heterozygous, and the heterozygous parents are carriers of the causative gene, and the galactose-1-phosphate uridine The transferase activity is only 50% of that of normal people. The galactose-1-phosphate uridine transferase deficiency in the body is mainly caused by point mutation of GALT. At present, dozens of mutation sites have been found, due to the decrease of enzyme activity, Lead to a significant increase in blood galactose-1-phosphate concentration, excessive galactose-1-phosphate accumulated in the brain, liver, renal tubules and other tissues, can interfere with normal metabolism and cause organ damage, in addition, galactose 1-phosphoric acid can also inhibit the activity of phosphoglucose mutase, glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, etc., preventing the decomposition of glycogen into glucose, causing hypoglycemia, galactose-1- Increased phosphoric acid leads to normal metabolism of galactose Resistance, causing the concentration of galactose in the blood to increase, the metabolism of galactose bypass is increased, and the production of galactitol is also increased. The deposition of galactitol in the crystal causes cataract.
Prevention
Galactosemia prevention
The main measure of prevention is the removal of lactose and other galactose-containing substances from food. High-risk pregnant women should limit lactose and other galactose-containing substances in food to reduce damage to the fetus.
Complication
Galvanose complications Complications
Childhood can have neurological deafness, a small number of patients can have retinal and vitreous hemorrhage, jaundice and liver enlargement, cirrhosis, ascites, liver failure, hemorrhage, Escherichia coli sepsis, growth retardation, intelligent development, high Chlorinated acidosis, proteinuria, amino aciduria and hypoglycemia.
Symptom
Symptoms of galactosemia Common symptoms Congenital lactase deficiency jaundice diarrhea nausea proteinuria hypoglycemia galactosemia bloating congenital lactose intolerance lactose intolerance
1. Acute course: Most children have galactose in breast milk or artificially fed milk for several days after birth, such as refusal, vomiting, nausea, diarrhea, weight loss, liver enlargement, jaundice, bloating, hypoglycemia, protein Urinary, etc., those who have the above performance should consider the possibility of galactosemia, need to carry out relevant laboratory tests, if it can be detected in time and take corresponding measures, cataract and mental retardation can occur quickly.
2. Mild disease course: There are no acute symptoms, but dysphonia, cataract, mental retardation and cirrhosis gradually appear with age.
3. Others: such as pseudo-cerebral tumors, for a rare manifestation, this system of galactose accumulated in the brain, followed by conversion to galactitol sputum caused by cerebral edema and increased intracranial pressure.
Examine
Examination of galactosemia
Laboratory inspection
1. Urine galactose test urine sugar positive, glucose oxidase method urine sugar negative, paper chromatography can identify it as galactose.
2. Neonatal screening for galactosemia: Screening for defective enzymes by Beutler method, observing the presence or absence of fluorescence, as the basis for the final evaluation, the disease has no fluorescence, and the defects of enzyme activity can also be obtained from the liver and intestine. Mucosa, fibroblasts and white blood cells are reflected.
3. Determination of blood galactose concentration: The normal concentration is 110-194 mol/L (using galactose oxidase or galactose dehydrogenase method), and the blood concentration of the patient is increased.
4. Determination of urinary galactose and galactitol concentration: can be determined by enzymatic method.
5. Red blood cell 1-galactose determination.
6. Determination of galactose metabolism related enzymes: This is an important basis for the diagnosis of this disease.
7. Non-specific biochemical indicators: such as proteinuria, glucose and urine.
Auxiliary inspection
1. Select B-mode based on clinical manifestations.
2. The fetal blood is taken by fetal mirror to measure the enzyme activity, the content of galactitol in amniotic fluid and the activity of enzyme in amniotic fluid cells are determined. The mutation analysis of the enzyme gene can be used for prenatal diagnosis of the fetus.
3. The galactose breath test can quantitatively determine the conversion of 13C-galactose to 13CO2 to understand the body's ability to oxidize galactose. Berry et al. reported the results of 37 cases of galactosemia (GALT deficiency), such as erythrocyte GALT activity. Very low (8.47%, normal 28.23%) indicates that the enzyme is severely defective.
Diagnosis
Diagnosis and identification of galactosemia
Note that the identification of infantile hepatitis syndrome, infantile hepatitis syndrome liver function damage is obvious, jaundice is mainly caused by elevated direct bilirubin.
