Glycogen storage disease type V

Introduction to glycogen storage disease type V Glycogen storage disease is a disease caused by excessive metabolism of glycogen in tissues due to metabolic disorders of hereditary glycogen, which is different according to the enzyme deficiency causing glycogen metabolism disorder and the excessive deposition of glycogen in the body. Glycogen storage diseases are classified into 11 types. Glycogen storage disease type V, also known as McArdle myopathy, is caused by a lack of muscle phosphorylase. The main clinical feature is pain, spasm and weakness after intense muscle contraction. basic knowledge The proportion of illness: 0.005% - 0.009% Susceptible people: no specific population Mode of infection: non-infectious Complications: renal failure

Glycogen storage disease type V etiology

(1) Causes of the disease

The disease belongs to hereditary glycogen metabolism disorder, which is caused by the lack of phosphophosphase. It is reported in the literature that the disease is autosomal recessive, and the enzyme gene is located on autosome 11 (11q13), but some reports also believe that The disease is autosomal dominant.

(two) pathogenesis

Muscle contraction requires energy consumption. Energy is mainly decomposed into glucose by muscle glycogen, and aerobic decomposition produces a large amount of ATP. At rest, muscles store a small amount of creatine phosphate and ATP in muscle. After shrinking, it is consumed.

When the phosphorylase necessary for the first step of glycogenolysis is deficient, the glycogen cannot be reduced to glucose for metabolism. Therefore, after the stored limited phosphocreatine and ATP are consumed, the muscles are in a stiff state. I can't relax.

Muscle biopsy showed swelling of muscle fibers, degeneration and localized necrosis, increased sarcolemmal nucleus, polymorphonuclear cells and phagocytic cells in the interstitium. Electron microscopy showed many deposition of glycogen particles between the submucosa, between the muscle fibers and between the muscle fibers. Mitochondria swelled, degenerated, muscle fibers were accumulated by a large number of glycogen, but the morphology was normal; muscle fiber histochemical staining showed phosphorylase deficiency or complete disappearance.

Classification of glycogen storage diseases

Defective type 1.0 urinary diphosphate glucose-glycotransferase, clinical manifestations of hepatomegaly, hypoglycemia, congenital muscle weakness, decreased muscle tone.

2. Type I glucose-6-phosphonate deficiency, clinical manifestations of hepatomegaly, hypoglycemia, ketotoxicity, acidosis.

3. Type II -1,4-glycosidase deficiency, heart enlargement, heart failure, giant tongue, muscle weakness.

4. Type III polysaccharide-1,6-glucosidase and/or fructose-1,41,4-transglucosidase deficiency, clinical manifestations of hepatomegaly, hypoglycemia, congenital muscle weakness, decreased muscle tone.

5. Type IV polysaccharide-1,41,6-transglucosidase deficiency, clinical manifestations of liver, splenomegaly, cirrhosis.

6. V-type muscle phosphorylase deficiency, clinical manifestations of muscle pain after exercise, weakness.

7. VI type liver phosphorylase deficiency, clinical manifestations of hepatomegaly, hypoglycemia.

8. Type VII phosphofructokinase deficiency, clinical manifestations of muscle pain after exercise, weakness.

9. VIII type hexose phosphate isomerase deficiency, clinical manifestations of muscle pain after exercise, weakness.

10. IXa type phosphorylase kinase deficiency, clinical manifestations of hepatomegaly, hypoglycemia.

11. IXb type phosphorylase kinase deficiency.

12. X-type phosphorylase kinase deficiency, clinical manifestations of muscle pain after exercise, weakness.

Glycogen storage disease type V prevention

Difficulties in the treatment of genetic diseases, unsatisfactory results, prevention is more important, preventive measures include avoiding close relatives marriage, implementation of genetic counseling, carrier genetic testing and prenatal diagnosis and selective abortion to prevent the birth of children.

Glycogen storage disease type V complications Complications, renal failure

Myoglobinuria, severe cases may have renal failure.

Glycogen storage disease type V symptoms common symptoms fatigue weakness proteinuria muscle atrophy

Clinical classification

According to the age of onset, it can be divided into:

(1) Children or juvenile onset, often manifested as muscle fatigue or intermittent myoglobinuria.

(2) Infants in early adulthood, characterized by post-exercise tendon and occasional transient myoglobinuria.

(3) Late-onset patients, who are onset at 40 to 50 years of age, are characterized by progressive muscle weakness, but have few myoglobinuria. Regardless of the type of McArdle myopathy, the following array of clinical symptoms are generally available.

2. Main clinical manifestations

(1) Sports tendon: After strenuous exercise, such as running, jumping, climbing, climbing, there is severe muscle pain, the lower limbs are obvious, the heavy ones can be accompanied by sweating, the muscle pain is improved after rest, the muscle pain lasts. From a few minutes to a few hours, even for several days, the intermittent symptoms disappear completely.

(2) Second wind phenomenon: refers to the phenomenon that the muscle spasm or muscle pain still adheres to mild to moderate physical activity, and the muscle spasm gradually reduces or disappears. The reason is not clear.

(3) Muscle fatigue and muscle weakness: muscle fatigue and weakness after strenuous exercise can persist, severe limbs can not move, and even eye muscles also fatigue, but this time with myoglobinuria, muscle weakness The distribution is similar to muscular dystrophy.

(4) Myoglobinuria after exercise: It is seen in 1/3 to 1/2 patients, which occurs within 1 to several hours after strenuous exercise, and the duration is within 48 hours. Myoglobinuria rarely occurs in late onset.

(5) Muscle atrophy and muscle hypertrophy: Mild fat of the gastrocnemius muscle accounts for more than half of the cases in this group, which is caused by the deposition of glycogen in the muscle fibers, and muscle atrophy is seen in the late stage of the disease.

Glycogen storage disease type V examination

1. Serum CPK, LDH is normal or slightly elevated.

2. Increased myoglobin content in blood and urine.

3. QRS increased on the ECG, RP extension and T wave inversion.

4. EMG examination of normal or myogenic changes After repeated electrical stimulation, evoked potential decline and muscle spasm.

5. Muscle biopsy showed swelling of muscle fibers, degeneration and localized necrosis, increased sarcolemmal nucleus, and polymorphonuclear cells and phagocytic cells in the interstitium.

Diagnosis of glycogen storage disease type V

diagnosis

1. According to the clinical characteristics of muscle spasm, pain, muscle weakness after exercise, the disease can be diagnosed.

2. The forearm ischemic exercise test can help diagnose the disease by placing the sphygmomanometer cuff on the upper arm of the patient. After inflation, the pressure inside the balloon is maintained at 26.6 kPa to prevent blood flow, and then the patient is allowed to perform distal limb movement ( Fist, pinch force meter, etc.) 1 min, after which the venous blood was taken at the 3rd, 5th, and 10th minutes to measure the lactic acid content. The blood lactic acid content after exercise was more than 3 times higher than that before exercise. Normal, McArdle myopathy patients No change, the positive rate of this method can reach 92.5%.

Differential diagnosis

Diagnosis should be differentiated from alcoholic myopathy, ischemic myopathy and myoglobinuria. It also needs to be differentiated from painful myotonia and stiff syndrome in neuromuscular stiffness.

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