Mild clinical expression of myasthenia gravis associated with autoimmune thyroid diseases

Michele Marinó, Roberta Ricciardi, Aldo Pinchera, Giuseppe Barbesino, Luca Manetti, Luca Chiovato, Lewis E. Braverman, Bruno Rossi, Alberto Muratorio, Stefano Mariotti

Research output: Contribution to journalArticlepeer-review

Abstract

Myasthenia gravis (MG) may occur in association with autoimmune thyroid diseases (AITD). The aim of this study was to evaluate the features of MG associated with AITD compared to those of MG without AITD. A total of 129 MG patients (34 men and 95 women; age range, 11-81 yr) were subdivided into: group A, 56 MG patients with AITD [25 with autoimmune thyroidiris and 31 with Graves' disease (GD)]; group B, 21 MG patients with nonautoimmune thyroid diseases; and group C, 52 MG patients without thyroid disease. The severity of MG was ranked according to the Osserman score. Laboratory evaluation included assays for antithyroid and antiacetylcholine receptor (AchRAb) antibodies. Ocular MG (Osserman's class 1) was more frequent in group A (41.0%) than in group B (14.2%; P <0.03) or C (21.4%; P <0.03). Severe generalized MG (classes ≤2B) was more frequent in groups B (57.1% P <0.03) and C (51.9%; P <0.02) than in group A (28.5%). GD patients with clinical evidence of ophthalmopathy had a higher frequency (P <0.05) of ocular MG (57.8%) than GD patients without clinical ophthalmopathy (16.6%). Thymic disease was less frequent in group A (26.7%) than in group B (71.4%; P = 0.001) or C (59.7%; P = 0.001). The prevalence of thymic hyperplasia was 17.8%, 38.0%, and 40.3% in groups A, B, and C, respectively; the prevalence of thymoma was 8.9%, 33.4%, and 19.4%. When only patients with generalized MG were considered, thymic disease was less frequent (P <0.02) in group A (40.6%) than in the remaining groups (69.4%). AchRAb was more frequent in groups B (57.1%) and C (57.6%: P <0.03) than in group A (35.7%). In conclusion, MG associated with AITD has a mild clinical expression, with preferential ocular involvement and lower frequency of thymic disease and AchRAb. This supports the hypothesis that ocular and generalized MG are separate diseases with different spectra of associated diseases. Nonautoimmune thyroid diseases have no influence on the features of MG. The association of ocular MG and AITD might be due to a common autoimmune mechanism and/or a peculiar genetic background.

Original languageEnglish
Pages (from-to)438-443
Number of pages6
JournalJournal of Clinical Endocrinology and Metabolism
Volume82
Issue number2
DOIs
Publication statusPublished - 1997

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology, Diabetes and Metabolism

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