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Home arrow Environment arrow Inflammatory Disorders of the Nervous System: Pathogenesis, Immunology, and Clinical Management


Given current treatment, which combines cholinesterase inhibitors, immunosuppressive drugs, PE, IVIg, immunosuppressive therapy, and supportive care in an intensive care unit (ICU) setting (when appropriate), most patients with MG have a near-normal life span. Mortality is now 3-4%, with principal risk factors being age older than 40 years, short history of progressive disease, and thymoma. Prior to modem therapies, the mortality from MG was as high as 30-40%. Fortunately, in most cases the term “gravis” is no longer applicable to most patients.

Morbidity results from intermittent impairment of muscle strength, which may cause aspiration, increased incidence of pneumonia, falls, and even respiratory failure if not treated [14]. In addition, the medications used to control the disease may produce adverse effects.

Today, the only terribly feared condition arises when the weakness involves the respiratory muscles. Weakness might become so severe as to require ventilatory assistance. Those patients are said to be in myasthenic crisis.

The disease frequently presents (40%) with only ocular symptoms. However, the EOMs are almost always involved within the first year. Of patients who show only ocular involvement at the onset of MG, only 16% still have exclusively ocular disease at the end of 2 years.

In patients with generalized weakness, the nadir of maximal weakness usually is reached within the first 3 years of the disease. As a result, half of the disease-related mortality also occurs during this period. Those who survive the first 3 years of disease usually achieve a steady state or improve. Worsening of disease is uncommon after 3 years.

Thymectomy results in complete remission of the disease in a number of patients. However, the prognosis is highly variable.

A retrospective study of 38 patients with MG indicated that the disease, particularly late-onset MG, is associated with a high risk for cancers outside of the thymus, whether or not the patient also has thymoma [16]. Extrathymic neoplasms occurred in 12 of the study patients. All of these tumors were solid and heterogeneous to their organ of origin. Some of the tumors were diagnosed before and some after the patients were diagnosed with MG.

Altogether the tumors represented nine different types of neoplasm, as follows:

• Two each of squamous cell carcinoma of the mouth, invasive bladder cancer, and

prostate adenocarcinoma

• One each of basal cell skin cancer; lung, gastric, breast, and colon adenocarcinoma; and renal cell cancer

The only statistically significant variable among the patients was age, with the extrathymic tumors being found only in patients over 50 years. None of the patients with these neoplasms had thyroid disease or an autoimmune disease other than MG.

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