A 35-year-old Woman consults an Ophthalmologist because of Double Vision

35-year-old woman consults an ophthalmologist because of double vision and droopy eyelids. She also has complaints of generalized muscle weakness. IV injection of edrophonium dramatically, but only briefly, reverses her symptoms.

This patient’s probable disease has a pathophysiologic basis that is closest to that of which of the following conditions?

A. Bullous pemphigoid
B. Diabetes mellitus type 1 (some cases)
C. Idiopathic Addison disease
D. Insulin resistance
E. Systemic lupus erythematosus

The correct answer is D. Insulin Resistance

This patient has myasthenia gravis, which was suspected based on the woman’s clinical presentation and confirmed with the response to the short-acting anticholinesterase drug edrophonium. Myasthenia gravis is an autoimmune disease in which antibodies directed against the acetylcholine receptor of the muscle side of the neuromuscular junction block the ability of the receptor to bind to acetylcholine. Of the diseases listed above, only insulin resistance is produced by a similar mechanism, i.e. antibodies to insulin receptors block the receptors’ ability to bind to insulin.

Bullous pemphigoid (Choice A) is caused by antibodies directed against the basement membrane of the skin, which damage the basement membrane and cause blister formation.

Some cases of diabetes mellitus type 1 (Choice B) and idiopathic Addison disease (choice C) are characterized by humoral, and probably cell-mediated, reactions against the cells in the endocrine tissue.

Systemic lupus erythematosus (Choice E) has circulating and locally generated immune complexes mediating the pathophysiology.