myasthnia gravis重症肌无力.ppt

Myasthenia Gravis重症肌无力 ;Muscular Disorders;Disorders of the Neuromuscular Junction;Disorders of Muscle Fibers(Myopathies);I. Definition of Myasthenia Gravis ;Ⅱ. Etiology and Pathogenesis ;1.Reduced Number of Receptors and the Competitive Activity of Anti-AchR Antibodies ;Ach Binds AChR ; How the antibodies act at the receptor surface of the end plate and impair the neuromuscular transmission?;2.The role of thymus in pathogenesis of MG ;Both T and B cells from the myasthenic thymus are particularly responsive to the AchR, more so than analogous cells from peripheral blood. Moreover, the thymus contains “myoid cells”(resembling striated muscle) that express surface AchRs. Maybe a virus with tropism for thymic cells that have AchRs might injure such cells and induce antibody formation. ;Ⅲ. PATHOLOGY OF MG ; 2. Pathology of skeletal muscles: In about 50% of patients, muscles contain lymphorrhages, which are focal clusters of lymphocytes near small necrotic foci without perivascular predilection. （淋巴细胞的聚集） The major abnormalities of the neuromuscular junction in MG include (a) reduced length of the postsynaptic membrane, (b) shortening of the synaptic folds and (c) widening of the synaptic clefts .;Ⅳ. CLINICAL FEATURES OF MG;C. Symptoms: ⒈ the fluctuating nature of myasthenic weakness: The weakness varies in the course of a single day, sometimes within minutes, and it varies from day to day or over longer periods. The weakness worsens towards the end of the day. The factors known to increase weakness include exertion, hot temperatures, infections, emotional upsets, certain drugs (for example, aminoglycosides, phenytoin, local anaesthetics), surgery, menses, and pregnancy.;2. the distribution of weakness: （1）Ocular muscles(levator palpebrae and extraocular muscles) are affected first in about 40% of patients and are ultimately involved in about 85%---ptosis and diplopia （2）Facial or oropharyngeal muscles are affected---dysarthria, dysphag