also calledSkin muscle。A muscle located in the superficial fascia beneath the skin.
There is a special plate-like base under the skin of vertebrates, which is separated from the surface layer of skeletal muscles. Most of the starting points are trunk muscles, limb muscles or pharyngeal muscles, while a few start from the skeleton, but all end in the skin.When contracting, it only causes attached skin, scales, feathers, hair and other activities.
According to the location and source, it can be divided into trunk skin muscle and neck skin muscle.The former is innervated by spinal nerve, while the latter is innervated by facial nerve of brain nerve.The cervical skin muscles form the superficial and deep cervical sphincters.The superficial cervical sphincter is more developed in some animals, also known as the platysma, which forms the cervicocutaneous muscle and the faciocutaneous muscle.The musculature of the neck skin muscle runs longitudinally and is closely attached to the pectoralis and brachial muscles, and continues to the head to become the facial skin muscle.Facial muscle bundles run towards the mouth, separating the muscle bundles mixed with the muscles of the mouth and lower lip.The deep cervical sphincter is a semicircular muscle bundle that bypasses the ventral side of the neck.The main function of skin muscle is to tension and shake the skin;The facial muscles can also pull the oral corners backward.
2、 Related diseases and treatment
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1. Dermatomyositis (DM) is an autoimmune connective tissue disease characterized by involvement of skin and striated muscle.
2. Etiology and pathogenesis
The etiology of DM is still unknown, which is known to be related to genetics, tumor, drugs, chemicals, infection and immune mechanism.
3. Classification
The researchers divided the disease into 5 types: type I was polymyositis;Type ⅱ is dermatomyositis;Type III is PM/DM with malignant tumor (paraneoplastic dermatomyositis);Type ⅳ is juvenile dermatomyositis;Type V is PM/DM complicated with collagen vascular disease (overlapping syndrome).
4. Diagnostic criteria
Five diagnostic criteria for DM: ① symmetrical weakness of proximal limb muscles; ②The muscle biopsy was consistent with the histopathological changes of myositis; ③Serum creatinase increased, especially CK and aldolase, followed by LDH; ④Characteristic electromyographic changes: myogenic damage - short polyphase motor units and fibrillation, as well as abnormal high-frequency repetitive discharge; ⑤Characteristic skin lesions, namely Heliotrope rash and Gottron sign.DM can be diagnosed when clinically meeting the above three or four conditions (with skin lesions);PM can be diagnosed when 4 conditions are met (no skin lesions);When the two conditions are met (with skin lesions), it is very likely to diagnose DM;When three conditions are met (no skin lesions), it is very possible to diagnose PM;DM may be diagnosed when one condition (skin lesions) is met;PM may be diagnosed when 2 conditions are met (no skin lesions).Another researcher suggested that the following diagnostic criteria should be added when diagnosing DM: ① myalgia; ②Anti Jo-1 antibody is positive; ③Nondestructive arthritis or arthralgia; ④Inflammatory signs (fever, rapid erythrocyte sedimentation rate, etc.) appear throughout the body.
5. Clinical manifestations
Cardiopulmonary disease The incidence of pulmonary involvement in DM is 9%~30%, while the incidence of pulmonary dysfunction is about 40%, which mainly causes three diseases: ① interstitial pneumonia (41%); ②Diffuse alveolitis (36.2%); ③Occlusive organizing pneumonia (22.8%).The prognosis of DM complicated with interstitial pneumonia is worse than that of DM alone, and the mortality is only inferior to those of DM complicated with tumor.The activity of lactate dehydrogenase (LDH) in lung tissue is more than 4 times higher than that in serum, so the sudden increase of LDH indicates the presence of lung and pleural lesions. If LDH does not increase and Jo-1 antibody is positive, there is also a risk of interstitial lung lesions.DM without myopathy also has the possibility of fatal interstitial pneumonia, and the main indication of cyclophosphamide (CTX) pulse therapy is interstitial pneumonia.40% of patients with this disease have abnormal electrocardiogram (ECG), including changes of ST-T segment and Q wave, bundle branch block, congestive heart failure and arrhythmia.Although pericarditis is rare, cardiac tamponade can cause death, which should be paid attention to.When the myocardium is involved, the serum muscle enzyme can also be increased.Its clinical significance is that skin lesions can occur at the same time or before and after muscle weakness.
6. Treatment
The application of glucocorticoid and immunosuppressive agents All types of DM need to be treated with glucocorticoid, and even can be treated with glucocorticoid pulse therapy in serious cases. However, fluorocorticoids such as dexamethasone and triamcinolone are prone to cause muscle weakness in proximal muscles and pelvic muscles, which is called hormonal myopathy, so they are not suitable for the treatment of this disease.
Treatment of DM lesions:
The treatment methods include: ① external use of anti light drugs with high ultraviolet protection index (SPF); ②External use of glucocorticoids, especially highly effective glucocorticoids, is helpful in the treatment of skin lesions; ③Hydroxychloroquine 0.2 ～ 0.4 g/d (Additionally, 0.1 g/d of Atipine can be used); ④Low dose MTX (2.5~30mg per week) can be considered for those who resist conventional treatment, which can often reduce or even stop the use of glucocorticoid; ⑤Long wave ultraviolet (UVA) treatment; ⑥Thalidomide is effective for localized skin lesions; ⑦Patients with malignant erythema should be carefully checked for tumor, and the erythema can gradually subside after the tumor is removed.
