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Myasthenia gravis: a long term follow-up study of Swedish patients with specific reference to thymic histology
  1. Natalie Tsinzerling1,
  2. Ann-Kari Lefvert2,
  3. Georg Matell3,
  4. Ritva Pirskanen-Matell4
  1. 1
    Department of Medicine, Immunological Research Laboratory, Centre for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
  2. 2
    Department of Medicine and Immunological Research Laboratory, Centre for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
  3. 3
    Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
  4. 4
    Department of Clinical Neuroscience, Karolinska University Hospital, Stockholm, Sweden
  1. Dr Ritva Pirskanen-Matell, Department of Clinical Neuroscience, Karolinska University Hospital, SE-171 76 Stockholm, Sweden; ritva.matell{at}karolinska.se

Abstract

Background: Myasthenia gravis (MG) is an autoimmune disorder of neuromuscular transmission. The majority of patients show abnormal thymic histology.

Setting: The study was performed at the Myasthenia Gravis Centre, Karolinska University Hospital, and at the Immunological Research Laboratory, Centre for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden.

Patients and methods: Information was collected retrospectively from 1956 and prospectively from 1975 on clinical data, concomitant diseases, concentration of serum acetylcholine receptor antibodies (AChR-abs), immunosuppressive treatment (IS) and response to it, in 537 patients of whom 326 were thymectomised. Follow-up time was 1.5–50 years.

Results: Age at onset of MG increased from a median age of 24 years before 1975 to a median age of 61 years after 2000. Thymoma was found in 65, hyperplasia (HPL) in 185 and a normal thymus in 76 patients. The trans-sternal surgical approach for thymectomy was used in 255 patients (78%). In five patients with thymoma, MG appeared after thymectomy. Of 537 patients, 466 (87%) had circulating AChR-abs. IS was given to 300 (56%) patients, mostly those with thymoma (85%). In total, 441 patients (82%) showed an improvement. One-third of patients with HPL, a quarter of those with thymoma, one-fifth of those with a normal thymus and one-seventh of those not operated on went into remission.

Conclusion: The prognosis for the majority of patients with MG is favourable, irrespective of thymic histology. The cause may be the use of immunomodulating therapy.

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Footnotes

  • Competing interests: None.

  • Abbreviations:
    AChR-ab
    acetylcholine receptor antibody
    HPL
    hyperplasia
    IS
    immunosuppressive treatment
    MFT
    muscle fatigability test
    MG
    myasthenia gravis

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