Miasthenia gravis

Review

Autoimmune myasthenia gravis: emerging clinical and biological heterogeneity
Matthew N Meriggioli, Donald B Sanders

Acquired myasthenia gravis (MG) is an autoimmune disorder of theneuromuscular junction in which patients experience fluctuating skeletal muscle weakness that often affects selected muscle groups preferentially. The target of the autoimmune attack in most cases is theskeletal muscle acetylcholine receptor (AChR), but in others, non-AChR components of the neuromuscular junction, such as the muscle-specific receptor tyrosine kinase, are targeted. The pathophysiologicalresult is muscle endplate dysfunction and consequent fatigable muscle weakness. Clinical presentations vary substantially, both for anti-AChR positive and negative MG, and accurate diagnosis andselection of effective treatment depends on recognition of less typical as well as classic disease phenotypes. Accumulating evidence suggests that clinical MG subgroups might respond differently totreatment. In this Review, we provide current information about the epidemiology, immunopathogenesis, clinical presentations, diagnosis, and treatment of MG, including emerging therapeutic strategies.Lancet Neurol 2009; 8: 475–90 Department of Neurology and Rehabilitation, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA (M N Meriggioli MD); and Division of Neurology,Department of Medicine, Duke University Medical Center, Durham, NC, USA (D B Sanders MD) Correspondence to: Matthew N Meriggioli, Department of Neurology and Rehabilitation, 912 S. Wood Street, M/C 796,University of Illinois at Chicago, Chicago, IL 60612, USA mmerig@uic.edu

Introduction
Acquired myasthenia gravis (MG) is a prototypical, antibody-mediated autoimmune disorder of the neuromuscularjunction (NMJ).1 In most cases, it is caused by pathogenic autoantibodies directed towards the skeletal muscle acetylcholine receptor (AChR).2 In others, non-AChR components of the postsynaptic muscle...