Get access

Thymus histology and concomitant autoimmune diseases in Japanese patients with muscle-specific receptor tyrosine kinase-antibody-positive myasthenia gravis

Authors

  • R. Nakata,

    1. Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
    Search for more papers by this author
  • M. Motomura,

    Corresponding author
    1. Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
    • Correspondence: M. Motomura, Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan (tel.: +81 95 819 7265 or 7262; fax: +81 95 849 7270; e-mail:lems@nagasaki-u.ac.jp).

    Search for more papers by this author
    • RN and MM contributed equally to this paper.

  • T. Masuda,

    1. Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
    Search for more papers by this author
  • H. Shiraishi,

    1. Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
    Search for more papers by this author
  • M. Tokuda,

    1. Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
    Search for more papers by this author
  • T. Fukuda,

    1. Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
    Search for more papers by this author
  • T. Ando,

    1. Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
    Search for more papers by this author
  • T. Yoshimura,

    1. Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
    Search for more papers by this author
  • M. Tsujihata,

    1. School of Health Science, Nagasaki University, Nagasaki, Japan
    2. Nagasaki Kita Hospital, Nagasaki, Japan
    Search for more papers by this author
  • A. Kawakami

    1. Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
    Search for more papers by this author

Abstract

Background and purpose

The differences in the characteristics of thymus histology, coexisting autoimmune diseases and related autoantibodies between anti-muscle-specific receptor tyrosine kinase (MuSK)-antibody (Ab)-positive myasthenia gravis (MG) patients, and anti-acetylcholine receptor (AChR)-Ab-positive MG patients are not clearly defined.

Methods

The types of thymus histology, coexisting autoimmune diseases and associated Abs in 83 MuSK-Ab-positive patients nationwide were investigated and were compared with those in AChR-Ab-positive patients followed at our institute (n = 83). As for the autoantibodies associated with thymoma, titin Abs were measured.

Results

Thymoma was not present in any of the MuSK-Ab-positive patients but presented in 21 patients (25.3%) amongst the AChR-Ab-positive patients. Titin Abs were absent in MuSK-Ab-positive patients but positive in 25 (30.1%) of the AChR-Ab-positive patients. Concomitant autoimmune diseases were present in eight MuSK-Ab-positive patients (9.6%) amongst whom Hashimoto's thyroiditis and rheumatoid arthritis predominated, whereas 22 AChR-Ab-positive patients (26.5%) had one or more concomitant autoimmune diseases of which Graves' disease predominated.

Conclusions

Differences in frequency of thymoma and thymic hyperplasia, coexisting autoimmune diseases and autoantibody positivity between MuSK-Ab-positive and AChR-Ab-positive MG were indicated, suggesting that, in contrast with AChR-Ab-positive MG, thymus does not seem to be involved in the pathogenic mechanisms of MuSK-Ab-positive MG.

Ancillary