Insights into the classification of myasthenia gravis.

Abstract

BACKGROUND AND PURPOSE:

Myasthenia gravis (MG) is often categorized into thymoma-associated MG, early-onset MG with onset age <50 years, and late-onset MG with onset age ≥50 years. However, the boundary age of 50 years old between early- and late-onset MG remains controversial, and each category contains further subtypes. We attempted to classify MG from a statistical perspective.

METHODS:

We analyzed 640 consecutive MG patients using two-step cluster analysis with clinical variables and discrimination analysis, using onset age as a variable.

RESULTS:

Two-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 (p<0.01), whereas ocular MG and SPMG without thymic abnormalities showed onset age skewed toward an older age (p<0.001 and p<0.0001, respectively). The other 2 subtypes showed normal distributions. THMG appeared as the main component of early-onset MG, and ocular MG and SPMG without thymic abnormalities as the main components of late-onset MG. Discrimination analyses between THMG and ocular MG and/or SPMG without thymic abnormalities demonstrated a boundary age of 45 years old.

CONCLUSIONS:

From a statistical perspective, the boundary age between early- and late-onset MG is about 45 years old.

• Authors: Tetsuya Akaishi, Takuhiro Yamaguchi, Yasushi Suzuki, Yuriko Nagane, Shigeaki Suzuki, Hiroyuki Murai, Tomihiro Imai, Masakatsu Motomura, Kazuo Fujihara, Masashi Aoki, Kimiaki Utsugisawa
• Journal: PloS one (PLoS One) Vol. 9 Issue 9 Pg. e106757 ( 2014) ISSN: 1932-6203 [Electronic] United States
• PMID: 25192469 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Topics

• Adult
• Age of Onset
• Aged
• Cluster Analysis
• Female
• Humans
• Male
• Middle Aged
• Models, Statistical
• Myasthenia Gravis (immunology, pathology)
• Thymoma (complications, immunology, pathology)
• Thymus Neoplasms (complications, immunology, pathology)
• Young Adult