Glycogen storage disease type VI in children
Introduction
Introduction to the type VI of glycogen storage disease in children Glycogen storage disease VI (GSD-VI) is caused by defects in liver phosphorylase, which is rare. Most children in the early childhood showed liver enlargement and growth retardation, no symptoms of heart and skeletal muscle involvement; hypoglycemia, hyperlipidemia and ketone body increase were mild. With age, liver enlargement and growth lag are gradually improving, and often disappear during puberty. Most children do not need treatment. To prevent hypoglycemia, they can take several small meals or give a high-carbohydrate diet. basic knowledge The proportion of illness: 0.002% Susceptible people: children Mode of infection: non-infectious Complications: dyslipidemia
Cause
Pediatric glycogen storage disease type VI etiology
(1) Causes of the disease
The disease is caused by defects in liver phosphorylase, and most of them are partial defects.
(two) pathogenesis
Glycogen is a high molecular polysaccharide composed of glucose, which is mainly stored in the liver and muscle as spare energy. Normal liver and muscle tissues contain about 4% and 2% glycogen, respectively. The glucose ingested in the body is glucose kinase, glucose. Phosphoric acid mutase and uridine diphosphate glucose pyrophosphorylase catalyze the formation of uridine diphosphate glucose (UD-PG), and then the glucose molecule provided by UDPG by glycogen synthase as -1,4-glycoside The bonds are joined into a long chain; every 3 to 5 glucose residues are transferred by the branching enzyme to the 1,4-position of glucose to 1,6 positions, forming branches, and if expanded, eventually forming a macrostructure of the dendritic structure, The molecular weight of glycogen is up to several million, and the outermost layer of glucose has a long linear chain, and most of them are 10 to 15 glucose units.
The decomposition of glycogen is mainly catalyzed by phosphorylase, releasing glucose 1-phosphate from the glycogen molecule, but the action of phosphorylase is limited to 1,4 glycosidic bonds, and when there are only 4 glucose residues before the branch point It is necessary to transfer 3 of these residues to other linear chains by debranching enzymes (starch-1,6-glucosidase, amylo-1,6-glucosidase) to ensure that the action of phosphorylase continues, at the same time, The debranching enzyme can release a glucose molecule linked by the -1,6-glycosidic bond, so that the repeated requirement is to ensure the body's demand for glucose, and the -1,4-glucosidase (acid maltose) present in the lysosome The enzyme can also hydrolyze the linear chains of different lengths to become oligosaccharide molecules such as maltose. The defects of any of the above-mentioned glycogen synthesis and decomposition processes lead to various types of glycogen storage diseases with different clinical manifestations. The disease is caused by partial defects in liver phosphorylase, and therefore, the lesion is relatively light.
Prevention
Pediatric glycogen storage disease type VI prevention
The prevention of glycogen storage disease VI can refer to the prevention method of glycogen storage disease, which should include prevention of infection during pregnancy, avoiding old birth, close relatives, avoiding radiation, exposure to chemical substances, abnormal genetic material, etc., preventive eugenics measures:
1. Prohibit close relatives from getting married.
2. Premarital examination to discover genetic diseases or other diseases that should not be married.
3. The detection of the carrier is determined by group census, family survey and pedigree analysis, laboratory examination and other means to determine whether it is a genetic disease, and determine the genetic mode.
4. Genetic counseling.
5. Prenatal diagnosis of prenatal diagnosis or intrauterine diagnosis is an important measure of preventive eugenics.
Complication
Children with glycogen storage disease type VI complications Complications, dyslipidemia
There may be mild blood lipids and elevated transaminase, moderate growth retardation.
Symptom
Children with glycogen storage disease type VI symptoms common symptoms fasting hypoglycemia dyslipidemia liver swelling slow growth
There was no onset in the neonatal period or in infants and young children. There was no significant gender difference. It was clinically similar to glycogen storage disease type I and III, but it was milder than type I. The clinical manifestations were hepatic enlargement, which may have mild blood lipids. Increased transaminase, moderate growth retardation, hypoglycemia is rare, because the symptoms can sometimes lead to missed diagnosis, so some people think it is benign liver, no heart and skeletal muscle involvement symptoms, normal intelligence.
In addition to the above clinical manifestations, the diagnosis depends on laboratory results. In patients with white blood cells, phosphorylase reduction, decreased viability, or liver biopsy can be found in glycogen deposition.
Examine
Pediatric glycogen storage disease type VI examination
1. Biochemical abnormalities include hypoglycemia, ketoacidosis, lactateemia and hyperlipidemia, but to a lesser extent.
2. The glucose tolerance test presents a typical diabetes profile.
3. Adrenaline test subcutaneous injection of 1:1000 adrenaline 0.02ml / kg, before injection and 10, 20, 30, 40, 50, 60min after injection, respectively, blood glucose, normal blood sugar increased by 40% ~ 60%; glycogen There was no significant increase in blood glucose in patients with cumulative disease.
4. Glucagon test intramuscular injection of glucagon 30g / kg (maximum amount of 1mg), blood samples taken at 0, 15, 30, 45, 60, 90, 120min after injection, respectively, within 15 to 45 minutes of normal Blood sugar increased by 1.5 ~ 2.8mmol / L, the disease did not increase blood sugar in the fasting or after meals.
5. Liver biopsy is best diagnosed with liver tissue biopsy. For glycogen staining, glycogen is increased and specific enzyme activity is decreased.
6. Gene detection can be detected by DNA analysis of peripheral blood leukocytes.
Conventional X-ray, B-ultrasound and electrocardiogram examination can be found that the liver is large and there is no abnormality.
Diagnosis
Diagnosis and diagnosis of type 2 glycogen storage disease in children
The characteristics of clinical manifestations and laboratory and auxiliary examination features are helpful for the differentiation of GSD-I and GSD-III. The glucagon test shows that blood glucose does not increase, so it can be found that it is different from GSD-IX. The glucose tolerance curve is normal.
