Insights into the Classification of Myasthenia Gravis

Background and PurposeMyasthenia gravis (MG) is often categorized into thymoma-associated MG, early-onset MG with onset age MethodsWe analyzed 640 consecutive MG patients using two-step cluster analysis with clinical variables and discrimination analysis, using onset age as a variable.ResultsTwo-step cluster analyses categorized MG patients into the following five subtypes: ocular MG; MG with thymic hyperplasia (THMG); generalized anti-acetylcholine receptor antibody (AChR-Ab)-negative MG; thymoma-associated MG; and generalized AChR-Ab-positive (SP) MG without thymic abnormalities. Among these 5 subtypes, THMG showed a distribution of onset age skewed toward a younger age (pConclusionsFrom a statistical perspective, the boundary age between early- and late-onset MG is about 45 years old.