Pediatric pseudohypertrophic muscular dystrophy

Introduction to pediatric pseudo-hypertrophic muscle malnutrition Duchenne muscular dystrophy, including DMD (duchennemusculardystrophy, DMD) and BMD (beckermusculardystrophy, BMD), is an X-chromosome recessive allelic disease that originates in muscle tissue. basic knowledge Sickness ratio: 0.0001% Susceptible people: children Mode of infection: non-infectious Complications: arrhythmia heart failure epilepsy fracture

Causes of large muscle dystrophy in children with fake fat

Cause:

The molecular biology method has been used to locate the DMD gene on X chromosome Xp21.1~Xp21.3, and the disease-causing gene is dystrophin gene. It is the largest human gene discovered so far, about 2000kb or more, containing 79 exon coding. , a 14 kb transcribed region, studies have shown that 60% to 70% of DMD is due to gene deletion or repeated mutation.

Gene deletions are non-randomly distributed, mainly in the central region of the gene (80%), and a few occur at the 5th end (20%). Large gene deletions often start at the 5th end of the gene, and gene deletion results in an open reading frame. The destruction, leading to DMD performance, BMD patients, the missing gene maintains the translation reading frame, and can produce a protein with half function and shortened length. The "reading frame" hypothesis explains 92% of patients with different DMD/BMD clinical Types of.

Dystrophin is part of the dystrophin glycoprotein complex (DGC), a complex of membrane-associated proteins that spans the sarcolemma, which binds to the cytoskeleton and extracellular matrix of cells, duchenne muscular dystrophy patients, and DGC due to the absence of dystrophin The reduction of composition, although it can be synthesized normally but not correctly assembled and integrated into the muscle fiber membrane, it is speculated that due to the damage of DGC, a series of chain reactions are triggered, leading to the necrosis of DMD muscle cells, and the lack of dystrophin makes the muscle fiber under the membrane. The association between the cytoskeleton and the extracellular matrix is disrupted, resulting in instability of the muscle fiber membrane, tearing of the membrane, and necrosis of myocytes.

Prevention of large muscle dystrophy in children with fake fat

Because the disease-causing gene of this disease is located in Xp21.1, the dystrophin is lacking. At present, no specific treatment for reversing the course of the disease has been found. Therefore, effective measures should be taken to reduce the disease in the population. The genetic load reduces the incidence of this disease.

1. Check out the carrier to find the carrier very early, guide their marriage and birth, can reduce the birth of children with progressive muscular dystrophy and carriers, there are many ways to detect carriers, such as family survey, serum enzyme activity Measurement, electromyography and muscle biopsy, etc., in which the determination of serum CPK and CPK-MB activity is the most simple and practical, the combination of the above methods can improve the positive rate of the detected carriers.

2. Prenatal diagnosis of sexually linked recessive hereditary history or carriers or women who have already had a child, in pregnancy, such as a baby boy, affected by about half of the population, at this time can take placental serum for CPK determination, such as If the elevation is obvious, or the pathological gene is positive by PCR, it should be induced by artificial abortion. If it is negative or is a baby girl, it can be born.

3. The purpose of neonatal screening is to detect children and carriers early, and to determine CPK activity after 6 to 10 weeks after birth is preferred.

Pediatric fake hypertrophy complications Complications arrhythmia heart failure epilepsy fracture

Heart failure and arrhythmia, acute gastric dilatation, epilepsy, prone to emotional/behavioural problems, cognitive decline and learning difficulties, fractures, etc.

Symptoms of large muscle dystrophy in children with common symptoms Muscular atrophy "Duck step" gait limb weakness, easy to fall, squat, difficulty, arrhythmia, heart failure, mental retardation, two arms can not be lifted, abnormal scapular sacral reflex

1. Skeletal muscle DMD patients with childhood onset, generally walking at 4 to 6 years old, easy to fall, running difficult, gradually appearing walking and going upstairs difficult, squatting station difficulties, nervous system examination can be seen lower limb muscle strength, muscle atrophy, The sputum reflex is weakened, and the pelvic muscles are weak and the typical duck steps, the shoulder muscles atrophy and weak formation of the wing-like shoulder or free shoulder, the atrophy of the abdominal muscles and the iliopsoas muscles form a characteristic Gowers sign, the vast majority of children have The gastrocnemius pseudo-hypertrophy, a small part of the tongue muscle or deltoid pseudohypertrophy.

2. Most patients with DMD have no cardiovascular symptoms. Heart failure and arrhythmia occur only in the late stage of disease and repeated stress, and there is little obvious congestive heart failure.

3. The smooth muscles of the gastrointestinal tract can also be affected. Acute gastric dilatation can lead to death. The autopsy of patients who die from this disease shows that the outer layer of the longitudinal muscle of the stomach has degenerative changes, and some patients may have severe constipation.

4. Patients with nervous system DMD and BMD may have central nervous system dysfunction, especially mental retardation. The average IQ of patients is below 1 standard deviation of normal value. The neuropathological mechanism of intelligent retardation is not yet clear, whether it is due to dystrophin protein in muscle. It is related to the expression of the central nervous system. It has not been confirmed. Some studies have reported that the incidence of epilepsy is increased, especially in the BMD type. DMD patients are prone to emotional/behavioural problems, cognitive decline and learning difficulties.

5. Other Larson et al. suggested that the DMD patients who were able to walk had a slight decrease in lumbar spine bone density, while those who could not walk were significantly lower. The data showed that 44% of the children had fractures, and 44% of the children who were still able to walk were fractured. Can't walk anymore.

Examination of large muscle muscular dystrophy in children

1. Serum biochemical examination of creatine phosphokinase (CK) is significantly increased, reaching 15,000 to 20,000 U / L, or even higher, elevated serum CK can occur at birth, slightly reduced in the later stages of the disease.

2. Muscle biopsy The characteristic pathological changes are scattered degeneration and necrotic muscle fibers. Over time, there is an increase in endometrial connective tissue and loss of muscle fibers, and replacement of adipose tissue.

3. Gene diagnosis DMD gene is located in Xp21.1-21.3, the protein encoded by the gene is dystrophin. After the 1990s, the domestic large hospitals used nuclear-staining Southern blot hybridization, and the polymerase chain reaction (PCR) lacking the hotspot exon. Analyze the gene for diagnosis. The detection rate of deletion is 56.7%-63.0%. The PCR analysis of primers using DMD gene deletion hotspot 9 is 47.5%~49.6%. The quantitative PCR has been applied in China. The short tandem repeat linkage analysis detected the DMD gene carriers, and there is still no systematic study on the diagnosis of point mutation DMD.

Electromyography: for myogenic changes, the muscles of the lesions are low, the duration of the waveform is shortened, and the multiphase waves are increased. Others should be examined by electrocardiogram and EEG.

Diagnosis and diagnosis of large muscle dystrophy in children with fake fat

Typical clinical manifestations and special genetic patterns are the basis of diagnosis, but laboratory tests are the basis for determining the diagnosis of this disease.

The natural course of the disease can distinguish between DMD and BMD. The clinical manifestations of BMD are similar to those of DMD, but the age of onset is slightly later, the progress is slow, the condition is mild, the prognosis is better, and the survival time is longer.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.