Résumé :
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Introduction : Epidemiological data showed that 10-20% of myasthenic patients have a thymoma. Object: to report cases of myasthenia gravis revealing invasive thymoma, and to specify the particularities of the association myasthenia gravis-invasive thymoma. Methods: a retrospective analysis of cases of myasthenia gravis treated between 1998 and 2008. Results: we compiled 70 cases of Myasthenia gravis. 15 were associated with thymoma, which 5 were invasive. Sexe ratio of these was 2/3. Mean age was 32,8. Thoracic scanning showed a limited thymic mass in 4 cases, with invasion of vascular structures in one case. All patients had thymectomy. Thymoma was graded B1 according to the WHO histological classification in 4 patients, B3 in one patient, and was considered benign in one case after the first thymectomy, then was graded B1 at the second histological examination during a relapse 5 years later. 2 patients died following a worsening of myasthenia after 5 and 6 months, and 2 patients received an adjuvant radiotherapy-chimiotherapy. The current decline is 1, 2 and 5 years. Discussion and conclusion: The occurence of myasthenia in patients with thymoma usually precedes the diagnosis of thymic neoplasm. Thymomas are considered a negative prognostic factor for myasthenia gravis because of greater severity of symptoms and reduced responsiveness to treatment. Thymoma-myasthenia has a worse prognosis than non thymoma-myasthenia, because of higher frequency of generalized disease with bulbar signs at onset, and higher frequency of immunosuppressive treatment.Thymoma patients with myasthenia had a better survival and a lower rate of recurrence than those without myasthenia.
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