Differential Diagnosis of Myasthenia Gravis

Disorders that may cause symptoms similar to MG include botulism and Lambert Eaton syndrome. Botulism results from Clostridium botulinum infection, which can also block AChR and cause muscle weakness.

Lambert Eaton syndrome is associated with certain types of lung cancer. This condition produces EMG results that are different than those produced by MG.

Medications can block the neuromuscular junction and cause symptoms similar to MG. These drugs include the following:

  • Antibiotics (e.g., ciprofloxacin, erythromycin, ampicillin)
  • Antispasmodic drugs (e.g., trihexyphenidyl; used to treat movement disorders)
  • Beta-adrenergic receptor blocking agents (e.g., propranolol, timolol)
  • Cardiac drugs (e.g., procainamide, verapamil, quinidine)
  • Lithium (may be used to treat bipolar disorder)
  • Penicillamine (penicillin product; used to treat metal poisoning)

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 01 Jan 2000

Last Modified: 25 Sep 2015