Acetylcholine receptors and myasthenia gravis

Ocular myasthenia: a protean disorder

Ocular myasthenia is a localized form of myasthenia clinically involving only the extraocular, levator palpebrae superioris, and/or orbicularis oculi muscles. Ocular manifestations can masquerade as a variety of ocular motility disorders, including cranial nerve and gaze palsies. A history of variable and fatiguable muscle weakness suggests this diagnosis, which may be confirmed by the edrophonium (Tensilon) test and acetylcholine receptor antibody titer. Anticholinesterases, corticosteroids and other immunosuppressive agents, and other therapeutic modalities, including thymectomy and plasmapheresis, are used in treatment. As the pathophysiology of myasthenia has been elucidated in recent years, newer treatment strategies have evolved, resulting in a much more favorable prognosis than several decades ago. This review provides historical background, pathophysiology, immuno-genetics, diagnostic testing, and treatment options for ocular myasthenia, as well as a discussion of drug-induced myasthenic syndromes.

Receptors in disease: an overview

Hormones and certain other signal molecules bind to plasma membrane or intracellular receptors producing signals that initiate their physiological effects. Recent understanding of receptors has resulted in recognition of several categories of receptor-related abnormalities. (a) Congenital receptor abnormalities such as receptor deficiency syndrome. LDL receptor defect in familial hypercholesteremia and primary androgen resistance are examples. (b) Postreceptor coupling abnormalities such as pseudohypoparathyroidism type Ia where there are reduced levels of guanine nucleotide receptor cyclase coupling protein. (c) Acquired receptor abnormalities, such as presence of circulating antireceptor antibodies. Such antibodies have been implicated in the pathophysiology of many diseases including Graves' disease and myasthenia gravis.