Myasthenia Associated with Other Autoimmune Diseases: A Series of Cases

We report four observations of myasthenia gravis associated with other autoimmune diseases. Myasthenia gravis can be associated with all autoimmune diseases with a predominance of dysthyroidism. Among the autoimmune diseases associated with myasthenia gravis in our series, there were associations with hyperthyroidism, sjogren syndrome, Biermer’s disease. You would have to know how to look for another autoimmune disease in front of all myasthenia gravis by looking for the slightest sign of appeal that could point you towards another pathology.


Introduction
Myasthenia gravis is defined as an autoimmune disease affecting the neuromuscular junction. It can be associated with almost all autoimmune diseases. Its incidence is globally low, from 100 to 200 for 1 million inhabitants and its association with other autoimmune diseases is also rare [1]. The association with dysthyroidism is the most common with 5% to 10% of cases, however, other autoimmune diseases can be found [2]. We report 4 observations of myasthenia associated with other autoimmune diseases. The evolution was marked by a progressive recovery of motor skills and complete recovery at 6 months at the 4 limb level, but persistence of a more pronounced facial diparesis on the left and the regression of fatigability under medical treatment.
Myasthenia gravis was generally stable under corticotherapy and azathioprine, the management of the syndrome of sjogren was more difficult with many related complications.
Observation 3 This is a 20-year-old nulligravid patient followed for Graves' disease diagnosed in June 2010 and put on Carbimazole: 30 mg/day combined with Propanolol: 20 mg/day. Anti Ssa and SSb Ab were positive and salivary gland biopsy recovered to Chisholm stage III. The electromyogram showed a switchboard compatible with myasthenia ( Figure 4).
Thoracic CT did not find a thymoma. The diagnosis of myasthenia gravis associated with Sjogren syndrome has been made.
Myasthenia gravis was generally stable under corticotherapy and azathioprine.

Discussion
Myasthenia gravis is an autoimmune disorder of the neuromuscular junction that can be associated with other autoimmune diseases. The diagnosis of all 4 observations was based on international consensus diagnostic criteria [3] [4] Open Journal of Internal Medicine  [5]. There is a female predominance of these affections and this tendency is found with these patients that are all female. All autoimmune diseases can be associated with Myasthenia. Dysthyroidism remains the most commonly diagnosed condition with 5% to 10% of patients [2] and dysthyroidism is found in 3 of our 4 patients. With regard to autoimmune diseases described (Graves' disease, Biermer's disease, Sjogren's syndrome), their association with myasthenia remains rarely described [2]. Dysthyroidism remains the most common condition and its frequency is higher in myasthenic patients than in the general population [6]. The association myasthenia and Biermer's disease remains very poorly described in the literature. There are however rare cases of isolated associations and in the series of Goulon et al. [6], as Fraissse et al. [7], there were proportions respectively of 3/84 patients who developed intrinsic anti-factor antibodies without any patient having developed an authentic Biermer's disease and 2/45. The association with Sjogren's syndrome, however, remains rarely described with 3 cases found in the literature; Indeed Dourov et al. [8] in France had described myasthenia gravis-associated with a thymoma and a malignant thymoma in 1968, in 2008 Sellami et al. [9] described another case associated with spondyloarthritis and a Gougerot and a third case was described by Tsai [10] associating a thymoma myasthenia and Sjogren syndrome. In our series of cases, we report a greater number of associations with sjogren syndrome, which is much more rarely described in the literature.
Myasthenia gravis illustrates the involvement of the thymus in autoimmune diseases because of its frequent association with thymic abnormalities and the important role of the thymus in its pathogenesis [11] even though in our series no patient presented a thymoma. The therapeutic strategies related to myasthenia were respected in the 4 patients [2]. All of our patients received prostigmine with intolerance in one patient, corticosteroid therapy was also instituted in all patients with definitive discontinuation in 2 patients. Azathioprine was initiated in 2 of our patients and weaning with corticosteroids was possible in these 2 patients despite the associated dysimmunity. High dose corticosteroids may achieve remission of both pathologies. In our cases, we started with a low dose of steroids, because a transitory worsening of MG that is sometimes observed on initiation of corticosteroids would have carried significant risk.

Conclusion
The association myasthenia and other diseases are not exceptional but are still poorly described in the literature. Dysthyroidism remains the most frequent in our series and in rare and isolated series in the literature. The search for other autoimmune diseases will depend on the clinical context even if the search for autoimmune dysthyroidism and thymoma should be systematic because of their frequent association with myasthenia.