title: Thymus histology and concomitant autoimmune diseases in Japanese patients with muscle-specific receptor tyrosine kinase-antibody-positive myasthenia gravis.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Clinical Neuroscience and Neurology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Nakata
authors.forename: M
authors.initials: M
authors.lastname: Motomura
authors.forename: T
authors.initials: T
authors.lastname: Masuda
authors.forename: H
authors.initials: H
authors.lastname: Shiraishi
authors.forename: M
authors.initials: M
authors.lastname: Tokuda
authors.forename: T
authors.initials: T
authors.lastname: Fukuda
authors.forename: T
authors.initials: T
authors.lastname: Ando
authors.forename: T
authors.initials: T
authors.lastname: Yoshimura
authors.forename: M
authors.initials: M
authors.lastname: Tsujihata
authors.forename: A
authors.initials: A
authors.lastname: Kawakami
mesh_terms: D000328:Adult; D044466:Asian People; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D001324:Autoantigens / Q000097:blood / Q000276:immunology*; D001327:Autoimmune Diseases / Q000150:complications*; D064211:Connectin / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000150:complications* / Q000276:immunology / Q000473:pathology; D011863:Radioimmunoassay; D020794:Receptor Protein-Tyrosine Kinases / Q000276:immunology*; D011950:Receptors, Cholinergic / Q000276:immunology*; D013945:Thymoma / Q000150:complications / Q000473:pathology; D013950:Thymus Gland / Q000473:pathology*; D013952:Thymus Hyperplasia / Q000150:complications / Q000473:pathology; D013953:Thymus Neoplasms / Q000150:complications / Q000473:pathology
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D064211:Connectin; D011950:Receptors, Cholinergic; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases
keywords: associated autoimmune disease; muscle-specific receptor tyrosine kinase; myasthenia gravis; thymus; titin antibodies