Hostname: page-component-8448b6f56d-42gr6 Total loading time: 0 Render date: 2024-04-25T05:25:35.326Z Has data issue: false hasContentIssue false
  • English
  • Français

Pseudo-Myasthenia Gravis and Thymic Hyperplasia in Graves’ Disease

Published online by Cambridge University Press:  02 December 2014

Michael W. Nicolle
Michael W. Nicolle*
Affiliation:
Department of Clinical Neurological Sciences, University of Western Ontario, London Health Sciences Centre, 339 Windermere Road, London, Ontario, Canada N6A 5A5
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.
Background:

Diagnostic confusion between thyroid disease and myasthenia gravis (MG) can arise because the two may have similar clinical features, and also because of the more frequent coexistence of these autoimmune disorders in the same individual. In MG, autoantibodies directed against the acetylcholine receptor result in muscle weakness. Thymic pathology is well recognized in MG, with thymic hyperplasia frequent in early onset MG and thymoma more common in later onset MG. In Graves’ disease, autoantibodies against thyroid antigens result in hyperthyroidism. A seldom-recognized feature of Grave’s disease is the occurrence of an enlarged thymus (thymic hyperplasia) on chest CT, or of thymic lymphoid hyperplasia pathologically.

Case study:

This report describes a case in which the discovery of a mediastinal mass during imaging of the thyroid, and the presence of myasthenic-like symptoms, in a patient with Graves’ disease prompted investigations into whether the patient also had MG.

Results:

Despite symptoms which strongly suggested MG, subsequent investigations did not confirm the diagnosis, and treatment of Grave’s lead to a resolution of the symptoms and regression of the thymic enlargement seen on CT.

Conclusion:

The case study highlighted clinical similarities between Grave’s disease and myasthenia gravis which might cause diagnostic confusion, and also the investigations which are useful in order to differentiate the two diseases. In addition to common clinical features, the autoimmune diseases Grave’s disease and myasthenia gravis may both produce radiological thymic enlargement.

Résumé

RÉSUMÉ<span class='bold'><span class='italic'>Introduction:</span></span>

Il peut exister de la confusion entre la mal- adie thyroïdienne et la myasthénie grave (MG) quant au diagnostic parce que les deux entités peuvent avoir des caractéristiques cliniques similaires et également à cause de la coexistence plus fréquente de ces deux maladies auto-immunes chez le même patient. Dans la MG, des auto-anticorps dirigés con- tre les récepteurs de l’acétylcholine induisent une faiblesse musculaire. La pathologie thymique est bien reconnue dans la MG, les patients présentant fréquemment une hyperplasie du thymus dans la MG à début précoce et le thymome est plus fréquent chez les cas à début tardif. Dans la maladie de Graves, les autoanticorps dirigés contre des antigènes thyroïdiens induisent une hyperthyroïdie. Une manifestation de la maladie de Graves qui est rarement reconnue est la présence d’un thymus augmenté de volume (hyperplasie thymique) au CT du thorax ou d’une hyperplasie lymphoïde thymique à l’anatomopathologie.

<span class='italic'><span class='bold'>Étude de cas:</span></span>

Nous rapportons le cas d’un patient atteint de la maladie de Graves chez qui la découverte d’une masse médiasti- nale à l’imagerie de la thyroïde et la présence de symptômes ressemblant à la myasthénie ont motivé l’investigation de la possibilité que le patient ait également une MG.

<span class='italic'><span class='bold'>Résultats:</span></span>

En dépit de symptômes suggérant fortement la présence d’une MG, l’investigation n’a pas confirmé ce diagnostic et le traitement de la maladie de Graves a induit une résolution des symptômes et la régression de l’hypertrophie du thymus a été démontrée par CT scan.

<span class='italic'><span class='bold'>Conclusions:</span></span>

Cette étude de cas souligne les similitudes cliniques entre la maladie de Graves et la myasthénie grave, ce qui peut provoquer de la confu- sion quant au diagnostic, et indique également les investigations qui sont utiles pour différencier les deux maladies. En plus d’avoir des caractéristiques cliniques communes, ces deux maladies auto-immunes peuvent toutes deux donner des images radiologiques d’augmentation de volume du thymus.

Type
Case Report
Information
Canadian Journal of Neurological Sciences , Volume 26 , Issue 3 , November 1999 , pp. 201 - 203
Copyright
Copyright © The Canadian Journal of Neurological 1999

References

1. Murakami, M, Hosoi, Y, Negishi, T, et al. Thymic hyperplasia in patients with Graves’ disease. Identification of thyrotropin receptors in human thymus. J Clin Invest 1996; 98: 2228–2234.CrossRefGoogle ScholarPubMed
2. Hohlfeld, R, Wekerle, H. The thymus in myasthenia gravis. Neurol Clin 1994; 12: 331–342.Google ScholarPubMed
3. Lanska, DJ. Indications for thymectomy in myasthenia gravis. Neurology 1990; 40: 1828–1829.CrossRefGoogle ScholarPubMed
4. Weinberg, DA, Lesser, RL, Vollmer, TL. Ocular myasthenia: a protean disorder. Surv Ophth 1994; 39: 169–210.CrossRefGoogle ScholarPubMed
5. Gilchrist, JM, Massey, JM, Sanders, DB. Single fibre EMG and repet-itive stimulation of the same muscle in myasthenia gravis. Muscle Nerve 1994; 17: 171–175.CrossRefGoogle ScholarPubMed
6. Oh, SJ, Kin, DE, Kuruoglu, R, Bradley, RJ, Dwyer, D. Diagnostic sen-sitivity of the laboratory tests in myasthenia gravis. Muscle-Nerve 1992; 15: 720–724.CrossRefGoogle Scholar
7. Vincent, A, Newsom-Davis, J. Acetylcholine receptor antibody as adiagnostic test for mayasthenia gravis: results in 153 validated cases and 2967 diagnostic assays. J Neurol Neurosurg Psychiatry 1985; 48: 1246–1252.CrossRefGoogle Scholar
8. Beekman, R, Kuks, JBM, Oosterhuis, HJGH. Myasthenia gravis:diagnosis and follow-up of 100 consecutive patients. J Neurol 1997; 244: 112–118.CrossRefGoogle ScholarPubMed
9. Wortsman, J, McConnachie, P, Baker, JR, Burman, KD. Immunoglobulins that cause thymocyte proliferation from a patient with Graves’ disease and an enlarged thymus. Am J Med 1988; 85: 117–121.CrossRefGoogle Scholar
10. Bergman, TA, Mariash, CN, Oppenheimer, JH. Anterior mediastinalmass in a patient with Graves’ disease. J Clin Endocrinol Metab 1982; 55: 587–588.CrossRefGoogle Scholar
11. Ford, HC, Savage, T, Delahunt, JW. Anterior mediastinal mass and Graves’ disease. Thorax 1985; 40: 469–470.CrossRefGoogle ScholarPubMed
12. Allard, JC, Lee, VW, Franklin, P. Thyroid uptake of gallium in Grave’s disease. Clin Nucl Med 1988; 13: 663–666.Google Scholar
13. Wolfe, LK. Myasthenia gravis and Graves’ disease. South Med J 1988; 81: 1334–1335.Google ScholarPubMed
14. Fyfe, B, Domínguez, F, Poppiti, RJ Jr. Thymic hyperplasia. A clue tothe diagnosis of hyperthyroidism. Am J Forensic Med Pathol 1990; 11: 257–260.CrossRefGoogle Scholar