Introduction
Scapular muscular dystrophy(facio-scapulo-humeral type muscular dystrophy, FSHD) is an autosomal dominant genetic disease. The patient's muscle weakness mainly affects the facial muscles and the scapular muscles.
Cause
(1) Causes of the disease
The disease is an autosomal dominant genetic disease, and there are also sporadic cases.
(two) pathogenesis
Wi Jmenga et al first confirmed that the FSHD gene is located on chromosome 4, and further studies have shown that it is located at 4q35. In 1992, the study found that the fragment after digestion with EcoR1 was detectable with a specific probe (p13E-11). Go to a DNA fragment that is shorter than the normal population. This short segment is less than 35 kb in length, while the normal population is 300 kb in length. 85% to 95% of patients with clinical diagnosis of FSHD (whether familial or sporadic) have confirmed the presence of short fragments. Many studies have shown that the greater the loss of the 4q35 region (the smaller the short segment formed), the more severe the clinical manifestations. In general, sporadic patients tend to develop earlier and have shorter episodes than familial patients.
Although the relationship between the short 4q35 fragment and FSHD has been clarified, the precise gene mapping or the genes affected by this defect are not clear, and the exact relationship between the deletion and the disease is still unknown. One hypothesis is that the absence of heterochromatin leads to abnormal chromosome structure, which in turn changes the expression and function of genes in adjacent regions. Some FSHD patients have recombination in the vicinity of the missing site, supporting the above hypothesis. Therefore, the current research has turned to the establishment of genes on chromosome 4 and adjacent FSHD regions and their characteristics. In addition, some family patients with FSHD have nothing to do with chromosome 4, indicating that they are genetically heterogeneous.
symptom
The disease is autosomal dominant, and there are sporadic cases. It usually begins in adolescence, and its typical clinical manifestation is that the patient's muscle weakness mainly affects the facial muscles and the scapular muscles. Clinical symptoms can occur at any age from infancy to adulthood, often between the ages of 20 and 40. Infancy is the most severe form of this type. The disease is progressing slowly and many patients remain relatively stable for a considerable period of time.
The facial muscles are affected by closed eyes, the mouth can not be rubbed, the eyebrows, the wrinkles are difficult, and the lips are thickened. The facial muscles mainly involve the orbicularis muscle and the orbicularis oculi muscle. They are often asymmetrical. The patient has a strange twisted smile, a depression in the corner of the mouth, unable to pout, and facial expression is depressed and dull. When a patient is required to whistle, the lips are often characteristically horizontal or horizontal. The patient can't completely close his eyes, and the eyelids can easily open.
The scapular muscles are affected by the difficulty of lifting the upper arm and the scapular scapula. The affected scapular muscles include the latissimus dorsi, trapezius, rhomboid, and anterior serratus. At rest, the patient presented with a shoulder-shoulder posture, a shoulder forward, and a scapula rise. When the forearm is moved up or abducted, the shoulder blades often rotate forward and outward. Patients often exhibit activity disorders, especially those that require the application of scapular muscles, such as climbing trees, swinging golf clubs, throwing softball, and so on. About one-third of patients are asymptomatic and can only be diagnosed on the basis of physical examination.
Abdominal muscles can be affected early in the disease, but often pay attention to the late stages of the disease. The typical manifestation is that the muscles in the lower part of the abdominal wall are severely affected, causing the abdomen to protrude. 90% of patients may have Beevors sign (the patient flexes the neck while lying supine, the umbilicus can go up, and occasionally move down), which can be an early manifestation of suspicious patients, because other muscle diseases rarely occur. which performed.
The upper arm muscles are affected by the upper arm, and some cases can affect the lower limb and trunk muscles after a long time, but rarely involve the distal part of the limb. The disease progresses slowly and can develop at rest for several years. The distal anterior group of the thigh is often the earliest and most severely affected. Typical complaints include foot mopping while walking, or significant foot drop, resulting in frequent falls or gait instability. In a few cases, patients may have more severe pelvic limb muscle weakness, which affects the hip flexor and abductor muscles, resulting in early relatively heavier gait instability. The patient's bulbar, pharyngeal, extraocular and respiratory muscles are generally unaffected and swallowing function is unaffected.
diagnosis
Typical clinical manifestations and family history contribute to clinical diagnosis.
Identification
According to the genetic pattern, age of onset, progression of the disease and clinical manifestations, the classification of progressive muscular dystrophy should be classified and identified. The disease should be differentiated from the following progressive muscular dystrophy:
1. Dummy hypertrophy (DMD) This type is the most common in progressive muscular dystrophy, accounting for more than 90%, the most serious condition and the worst prognosis. Most cases have a chain of recessive inheritance, and some are autosomal recessive. Children often have a history of infantile developmental retardation, but most of the clinical symptoms begin to increase and gradually increase from 4 to 8 years old. The affected muscles gradually develop from near to far, and the process of disease progression is: limb weakness → difficulty in going up the stairs → difficulty walking on the ground → unable to walk. The most typical clinical manifestation is the Gower sign, which is the action process from the supine position to the upright position: the child first turns into a prone position, and then the hands hold the ground, knees, and waist to erect, this phenomenon is almost the only disease. Because the shoulder strap has muscle atrophy and weakness, when the arms are extended, the inside of the shoulder blade is far from the chest wall, like a bird wing, called a winged shoulder. In addition, pseudohypertrophy can be seen at the gastrocnemius or deltoid muscle. Muscle atrophy is progressive, the child is debilitating, and rarely survives to 20 years of age, most of which die from heart failure (because 80% of children have myocardial damage) or lung infection.
2. Limb band sex is autosomal recessive. Usually onset at 10 to 30 years old, first affecting the muscles of the pelvic girdle and scapula, the disease progresses slowly, usually only to the severity of middle age, and more without pseudo-hypertrophy.
3. The distal type and the eye muscle type are rare, more than the onset of adulthood.
complication
Patients usually do not have significant extramuscular involvement, but a large number of studies have confirmed that the incidence of high-frequency deafness and retinal vascular abnormalities in the FSHD population is gradually increasing, but often no clinical significance. Many studies have found that patients with FSHD have a tendency to develop atrial arrhythmias.
treatment
Western medicine treatment
There is currently no special treatment, and supportive care is the main treatment. Due to the different muscles involved, the patient is prone to shoulder, back, abdomen and leg pain. The conservative treatment, including non-steroidal anti-inflammatory drugs, appropriate exercise, and physical therapy can alleviate some discomfort complaints. The custom-made plastic squat-foot braces can reduce the sagging of the foot and stabilize the gait. Patients with significant abdominal or lower back pain or a combination of both can use a custom-made waist corset or belt to support the weak abdominal muscles.
There are currently no drugs that can improve the muscle strength of patients with FSHD or delay the progression of the disease. Used by scholarsPrednisoneEight patients with FSHD were treated, but the results showed no significant benefit.
prevention
No specific treatment has been found to reverse the course of the disease. Therefore, it should be emphasized that effective measures should be taken to reduce the genetic load of the disease in the population and reduce the incidence of the disease. If the carrier is detected, the marriage and birth are guided. There are many ways to detect carriers, such as family surveys, serum enzyme activity measurements, electromyography, and muscle biopsy. Among them, 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.
The purpose of neonatal screening is to detect children and carriers early. It is preferred to measure CPK activity 6 to 10 weeks after birth.
Prognosis
The development of muscle weakness is decreased, first involving the facial muscles, then moving down to the scapular and diaphragm muscles, and finally affecting the pelvic limb muscles, which has no significant effect on the patient's life span.
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