pediatric glycogen storage disease type Ⅲ
Introduction
Introduction to type III glycogen storage disease in children Glycogenstoragedisease (GSD) is a glycogen metabolism disorder caused by a congenital enzyme deficiency. Glycogenstoragydisease type III is a Cori type III glycogen storage syndrome, also known as Cori disease. , debranching enzyme deficiency, Forbes disease, limited dextrin disease (Limiteddextrinosis), debranching glycogen storage disease (Debrancherglycogenstoragedisease), Forbes syndrome. basic knowledge Sickness ratio: 0.05% Susceptible people: children Mode of infection: non-infectious Complications: splenomegaly cirrhosis hypoglycemia
Cause
Pediatric glycogen storage disease type III etiology
Causes:
At least 8 kinds of enzymes necessary for glycogen synthesis and catabolism have been confirmed, and glycogen storage diseases occur due to these enzyme defects, and can be classified into 12 types, among which types I, III, IV, VI, and IX Liver lesions are predominant, with liver damage of type I, III and IV being the most severe; type II, V, and VII are mainly muscle tissue damage, except for partial hepatic phosphorylase kinase deficiency, which is X-linked recessive inheritance. All are autosomal recessive genetic diseases. This disease is an autosomal recessive genetic disease caused by a lack of debranching enzymes.
Pathogenesis:
Debranching enzymes have two catalytic enzyme activities, namely starch-1,6-glucosidase (amylo-1,6-glucosidase) and oligo-(1,41,4)-glucanotransferase (oligo) -1,4-1,4-glucantransferase), whose coding gene is located at 1p21, when the glycoprotein outer glucose linear chain has only 4 glucose residues before the branch point, oligo-(1,41,4 - Glucan transferase transfers three of these residues to other linear chains to ensure that the action of phosphorylase continues; at the same time, the starch-1,6-glucosidase can be removed from the branch point with - 1,6-bonded glucose molecules, when the debranching enzyme is deficient, the glycogen decomposition cannot proceed normally, resulting in an increase in the number of 1,6 glycosidic linkages and an abnormal molecular structure of the glycogen, depending on the enzyme deficiency and the involvement of tissues and organs. In fact, the disease is divided into several subtypes: the children whose liver and muscles are deficient in enzyme activity are of type IIIa, the most common; only the lack of enzyme activity in the liver belongs to type IIIb, accounting for about 15%.
The pathological changes of liver tissue of this type are similar to those of GSD-I. The glycogen content of liver can be as high as 17%. However, this type has little fatty degeneration and fibrosis is obvious. It can be identified, and the glycogen accumulated in the muscle tissue is accumulated. Between myofibrils and muscle fiber membranes.
Prevention
Prevention of type III glycogen storage disease in children
Detection of debranching enzymes in cultured amniocytes or villous cells can provide a basis for prenatal diagnosis. Available methods include: 1 immunoblot analysis; 2 qualitative or quantitative methods of debranching enzyme activity, due to debranching enzymes in these two cells The vitality is relatively low, so it is technically difficult.
Complication
Pediatric glycogen storage disease type III complications Complications splenomegaly cirrhosis hypoglycemia
Growth retardation, splenomegaly, a small number of progressive myopathy, individual disease continues to develop into cirrhosis, liver failure, rare hypoglycemic episodes.
Symptom
Pediatric glycogen storage disease type III symptoms common symptoms slow growth fasting hypoglycemia symmetrical muscle weakness heart enlargement weakness ECG abnormal liver failure
The clinical symptoms of this type are much milder than that of GSD-I, and very few severe hypoglycemias occur. Children with growth retardation and hepatomegaly are the main complaints, and often have splenomegaly at 4 to 6 years old, but physical examination alone cannot be combined with GSD. -I phase identification, many children except the liver, muscle tissue is also involved, manifested as muscle weakness, especially when walking too fast or climbing, even tendon, a small number of progressive myopathy, lesions involving the myocardium Cardiac enlargement and abnormal electrocardiogram, but heart failure and arrhythmia are rare. The disease does not involve the kidney. Unlike GSD-I, some children have significantly reduced liver growth during puberty, and their growth and development have improved. The mechanism is unknown. The child's condition continues to develop to cirrhosis and liver failure.
Examine
Examination of type III glycogen storage disease in children
Serum transaminase was significantly increased in children, and the degree of increase in blood lipids was different. It was related to whether the episode of hypoglycemia was serious, and serum lactic acid and uric acid were generally normal.
The galactose and fructose tolerance test is normal. Because the gluconeogenesis mechanism of the child is normal, the protein or amino acid can increase the blood sugar. The glucagon or adrenaline test can also increase the blood sugar of the child 1 to 3 hours after the meal. However, if the test is carried out after 14 hours of starvation, there is no effect, indicating that the glycogen hydrolysis process is blocked to the branching point. The above functional test can be used as an auxiliary diagnosis, and the diagnosis is still based on the determination of the debranching enzyme activity in the liver and muscle. Some children may also have defects in glycogen accumulation and enzyme activity in peripheral red blood cells.
Conventional X-ray, B-ultrasound, electrocardiogram and electromyography, generally seen liver enlargement, spleen enlargement, or moderate hypertrophy and abnormal ECG.
Diagnosis
Diagnosis and diagnosis of type III glycogen storage disease in children
Fasting adrenaline or glucagon test response is poor, if you test after a few hours of eating, the reaction is normal, the determination of enzymes in red blood cells or white blood cells (de-branchase activity is significantly lower than normal people, most only 50% Or lower), can be clearly diagnosed, in addition, localized dextrin test: red blood cells, muscle or liver with localized dextrin, help diagnosis, glucagon test can be distinguished from von Gierke disease, the specific method is: In the case of this symptom, the blood glucose increased by 3 to 4 mmol/L (54 to 72 mg/ml) after intramuscular injection of glucagon 0.5 mg, and the lactic acid concentration did not change in the two tests.
Note that the identification of von Gierke disease, glucagon test, normal human injection of glucagon within 30min, blood glucose increased by at least 3.9mmol / L; and von Gierke disease blood glucose increased <1.7mmol / L, fasting and after eating This is the case, according to which GSD-III can be differentiated. The latter can be given glucagon 2 hours after a meal, and the blood glucose concentration will be significantly increased. The adrenaline tolerance test is not superior to the glucagon tolerance test and may cause Adverse side effects, feeding galactose or fructose to von Gierke patients does not lead to an increase in blood sugar levels. This tolerance test should be done as much as possible, which can lead to severe acidosis.
