Myasthenia Gravis: Basic Designs, Sample Sizes and Pitfalls

Abstract

Myasthenia gravis (MG) is a well-characterised antibody-mediated autoimmune disorder. The target of attack is the acetylcholine receptor (AChR) situated at the neuromuscular junction, and the resultant loss of AChRs leads to fatiguable weakness which is variable in distribution between patients. Patients with MG often respond dramatically to anticholinesterases, which increase the amount of acetylcholine (ACh) available to bind to the reduced number of AChRs. However this action is short-lived (hours) and has no effect on the underlying disease process. Immune manipulation with immunosuppressive drugs, plasma exchange (PE) and intra venous immunoglobins (IVIG) is more effective and, in the former case, longterm treatment for many patients. Clinical trials in MG aim to find the optimum of the present available treatments and the effectiveness of new, usually immune-modulating treatments.