Myasthenia gravis: a review

Abstract

Acquired myasthenia gravis is a relatively uncommon disorder, with prevalence rates that have increased to about 20 per 100,000 in the US population. This autoimmune disease is characterized by muscle weakness that fluctuates, worsening with exertion, and improving with rest. In about two-thirds of the patients, the involvement of extrinsic ocular muscle presents as the initial symptom, usually progressing to involve other bulbar muscles and limb musculature, resulting in generalized myasthenia gravis. Although the cause of the disorder is unknown, the role of circulating antibodies directed against the nicotinic acetylcholine receptor in its pathogenesis is well established. As this disorder is highly treatable, prompt recognition is crucial. During the past decade, significant progress has been made in our understanding of the disease, leading to new treatment modalities and a significant reduction in morbidity and mortality.

Figure 1

(a) Photograph of a patient with MG showing partial right ptosis. The left lid shows compensatory pseudolid retraction because of equal innervation of the levator palpabrae superioris (Herring's law). (b) Post-Tensilon test: note the improvement in ptosis (with permission from Kurukumbi et al. [5]).

Figure 2

CT chest image in a patient with MG revealing large necrotic mass in the left anterior mediastinum (white arrows) and bilateral hilar lymphadenopathy (with permission from Kurukumbi et al. [5]).