Myotonia congenita

Introduction to congenital muscle rigidity Congenital myotonia (congenital myotonia) is a hereditary myopathy characterized by myotonia and muscle hypertrophy. It is divided into autosomal dominant (AD) genetic and recessive (AR) genetic. Congenital myotonia (congenital myotonia) was first reported by Charles Bell (1832) and Leyden (1874). The Danish doctor Thomsen (1876) described in detail his own and his family's 4 generations and 20 members of the disease, which showed "free voluntary muscle rigidity. Sexual cramps, with hereditary mental disorders, mental disorders may be just accidental. basic knowledge Sickness ratio: 0.0001% Susceptible people: children Mode of infection: non-infectious Complications: depression

Congenital myotonia etiology

(1) Causes of the disease

The disease is currently considered to be a skeletal muscle ion channel disease caused by a mutation in the gene encoding the ion channel at the 7q32 site of the chromosome.

(two) pathogenesis

The disease lacks morphological changes, and the muscle rigidity of individual muscle fibers is very obvious. It is speculated that there may be physiological changes in the muscle fiber membrane or abnormal muscle fiber conduction structure. After the application of the arrow poison, the muscle rigidity will continue. The electromyogram shows that the contraction muscle fiber tension is slowly decreasing, which is tiny. The potential is persisted, and the stimulation of a single muscle fiber is found. Only continuous stimulation can obtain myogenic tonic discharge, and the myotonic muscle fibrillation potential is gradually reduced.

An in vitro study of myotonic goat muscles in an animal model of congenital myotonia found that hypertonic hyperexcitability (repetitive ignition and post-discharge) is caused by decreased chloride ion conductance in the transverse tube system, and human muscle tonic muscles also demonstrate reduced chloride conductance. The high excitability state of myotonic fiber membrane is associated with the reopening of abnormal sodium channels.

The disease-causing gene is located in the CLCN1 gene, which is a major part of the 7q32-encoded skeletal muscle chloride channel, including 23 exons. More than 30 point mutations and 3 gene deletions have been found (Plassart-Schies et al, 1998; Fred et al, 1999), Chlorine Channel gene mutation phenotypes include recessive and dominant, myotonic drug trials have found that blocking 50% of physiological chloride currents is not sufficient to produce tonic activity, which can explain recessive mutations (complete destruction of protein function). Although the current of chlorine decreased by 50%, the muscle rigidity did not appear in the clinic. The common activation curve of dominant myotonic chloride current drifted to the positive membrane potential, which caused the whole chlorine conductance to decrease, and sometimes the degree of drift was inconsistent with the clinical severity, such as Gin-552- Arg causes large potential shifts, but clinical manifestations are very light (Kubisch et al, 1998). Levior's myotonia is a dominant hereditary congenital myotonia, named by DeJong, with mild symptoms compared with Thomsen's disease. Later, Lehmann-Horn et al found that two patients with Levior myotonic pedigree had the same genetic defect chloride channel (CLCN1) mutation as Thomsen's disease. Therefore, Levior muscle rigidity seems to be light Tho. Msen is sick.

Congenital muscle rigidity prevention

The prenatal diagnosis of this disease is feasible amniotic fluid or chorion, villus tissue biopsy, detection of CTG repeats, but can not predict that the fetus with amplifying mutation is congenital or other types of myotonic dystrophy.

Congenital myotonia complications Complications depression

Patients with urinary sphincter involvement may have difficulty urinating, sometimes with psychiatric symptoms such as irritability, depression, solitude, depression and obsessive attitudes.

Congenital myotonia symptoms Common symptoms Limb movement incoordination Tendon muscle tension increased easy to fall gait muscle pseudo-hypertrophic muscle hypertrophy obsessive concept breathing difficulties dysphagia strabismus

1. Usually there is generalized muscle rigidity from birth, without muscle weakness and muscle atrophy, until early childhood symptoms progress, adulthood tends to be stable, muscle contraction produces rigidity, severe cases of muscle strength directly affect the whole body skeletal muscle, lower limbs Walking or running is limited, the patient's gait is squatting or falling, the upper limb muscles, the facial muscles and the trunk muscles are involved. If you force the fist or shake hands, you can't immediately release your hands. After the laughter, the expression muscles can't be immediately caught, often causing others to be confused. After chewing, you can't open your mouth. If you close your eyes, you can produce sputum when you sneeze. If you can't completely blink in a few seconds, some cases will have strabismus in the extraocular tendon. If you sit for a long time, you can't stand up immediately. It is difficult to climb the building. You can't start after standing still. It is difficult to get up at night when you get up. If you fall, you can't support it by hand. It looks like a door panel. If you suddenly cause a strong and straight fall due to sudden sound or shock, the recessive hereditary type is rare. The age of onset of Chinese patients is usually later than that of foreign countries.

2. Muscle fake hypertrophy is a prominent sign. The tent-shaped upper lip is like a "carping mouth". It can have different degrees of sucking, difficulty in swallowing, diaphragmatic weakness, bronchial aspiration, and jaw opening, forming a characteristic face. Newborns or children can identify the disease at a glance, can not sit up, start to learn to walk when the legs are stiff, crying or sneezing after blinking slow; diaphragm muscle, intercostal muscle weakness and lung development immature can cause breathing difficulties, It can lead to neonatal death. In Harper's study, there are 24 such deaths in the siblings of the patient. They may have mild to moderate mental retardation, common deformed foot or body joint distortion, and tend to be stable in adulthood.

3. The patient's whole body muscle hypertrophy looks like an athlete, but the muscles are stiff, the movement is awkward, the starting is difficult, the repeated movement can relieve the symptoms, and the cold does not aggravate the muscle rigidity. It is a characteristic of chloride channel disease, and sniper muscle rigidity can occur. Muscular spheroids or depressions, urinary sphincter involvement, dysuria, sometimes psychiatric symptoms, such as irritability, depression, solitude, depression and obsessive-compulsive effects, muscle muscles after repeated muscle movements are not alleviated, but aggravated, called abnormal muscle rigidity, Patients with this disease are rarely induced by continuous exercise. Those with muscle pain during myotonic attack are called type II muscle rigidity, smooth muscle and myocardium are not tired, and intelligence is normal.

4. Frequently inherited patients usually do not significantly aggravate during the course of the disease, often insidious inheritance can be slowly aggravated, and its symptoms often start from the lower limbs, and then spread to the upper limbs muscles and facial muscles, and may have a transient muscle weakness.

Examination of congenital muscle rigidity

1. Serum muscle enzyme test helps to differentiate the diagnosis.

2. Serum electrolyte examination helps to differentiate the diagnosis.

3. The EMG showed a typical myotonic potential. The early EMG of the baby showed strong tonic discharge, and about 1/3 of the patients had ECG changes.

4. Muscle fiber hypertrophy can be seen in muscle biopsy. The affected muscle is prone to central nucleation. The enlarged muscle fibers contain more normal structures of myofibrils. No obvious morphological changes were observed by electron microscopy.

Diagnosis and diagnosis of congenital muscle rigidity

diagnosis

According to family history, and the clinical manifestations of infancy or childhood begin to develop muscle contraction after tonic spasm, the whole body skeletal muscle is involved, symptoms can be alleviated after repeated exercise, with muscle hypertrophy, but muscle atrophy, muscle weakness can not be obvious, awkward movement Difficulty in starting, cold does not increase the rigidity of the muscles, slamming the muscles of the abdomen, sniper muscle rigidity, etc., as well as EMG findings, can be diagnosed.

Differential diagnosis

1. myotonic dystrophy (myotonic dystrophy): early childhood muscle weakness, muscle atrophy and muscle rigidity, the first two are more prominent, and have narrow face, baldness, cataract and endocrine dysfunction, etc., EMG is typical Muscle tonic potential, obvious muscle rigidity in infancy tends to congenital muscle rigidity, rarely this disease.

2. Congenital accessory muscle rigidity: from childhood onset, muscle rigidity is light, no muscle atrophy, muscle hypertrophy is not obvious, no muscle stimulation can also appear muscle rigidity.

3. Atrophic muscle rigidity: after puberty, there is obvious muscle atrophy, muscle weakness, with endocrine and nutritional disorders.

4. The disease must be associated with muscle fiber twitching, persistent muscle activity syndrome, painful sputum-muscle tremor syndrome, high potassium periodic paralysis, Schwartz-Jampel syndrome, pathological painful sputum syndrome, stiff Syndrome and phosphorylase or phosphofructokinase deficiency contraction, patients with these diseases have no snoring myotonia and typical EMG abnormalities, the only exception is Schwartz-Jampel syndrome, hereditary, stiff, with Short stature and hypertrophy may be a type of myotonia that should be distinguished from muscle fibrillation and persistent muscle activity syndrome, and another late-onset autosomal recessive generalized myotonia or Becker's disease, with distal mild muscle weakness and muscle atrophy, localizes to the 7q35 chromosome.

5. It should also be differentiated from certain drugs-induced muscle rigidity, such as depolarizers, muscle relaxants, anesthetics and drugs for the treatment of hypercholesterolemia, and rare beta-blockers or diuretics (especially during pregnancy). The effect is usually shorter.

6. Congenital muscle rigidity of hypertrophy and familial hyperplasia, hypothyroidism, multiple myopathy, hypertrophic polymyopathy and Bruck-DeaLange syndrome (congenital hypertrophy, mental retardation and extrapyramidal system) Identification of dyskinesia, hypothyroidism, electromyogram showed a strange high-frequency discharge (pseudo-muscle stiffness), obvious muscle edema, and other signs of hypothyroidism such as sputum reflex.

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