Neuromyelitis Optica in Patients With Myasthenia Gravis Who Underwent Thymectomy

Abstract

Background: Myasthenia gravis (MG) and neuromyelitis optica (NMO, also known as Devic disease) are rare autoimmune disorders, with upper-limit prevalence estimates in the general population of 15 per 100 000 and 5 per 100 000, respectively. To our knowledge, an association between these diseases has not been previously reported. Objectives: To describe 4 patients with MG who developed NMO after thymectomy and to analyze possible causes of apparent increased prevalence of NMO among patients with MG. Design: Case series. Patients: Four patients with MG who underwent thymectomy. Interventions: None. Results: The prevalence of MG within the published cohort of patients with NMO is more than 150 times higher than that in the general population. Conclusion: Dysregulation of B-cell autoimmunity in myasthenia, possibly exacerbated by loss of control over autoreactive cells as a result of thymectomy, may predispose patients to the development of NMO.

Demyelinating disease in patients with myasthenia gravis

“…This patient resembles those reported by Kister et al 9 , who suggested that unspecific immune dysregulation, either due to thymectomy or genetic susceptibility might influence the development of a second autoimmune disease. Although all our patients achieved a good control of myasthenia symptoms, we could not determine the influence of developing dd on MG control due to the small number of patients in this series.…”

“…The occurrence of dd in association to MG have been reported before, and are described as monophasic events (myelitis, acute disseminated encephalomyelitis and optic neuritis) [10][11][12][13] and recurrent diseases (multiple sclerosis, recurrent transverse myelitis and NMo) 7,[9][10][11][12]14 . some authors state that this association may not happen by chance, as the incidence of dd in patients with MG is much higher than expected in the general population 6,15 , and both may be part of multiple autoimmune syndromes or genetic predisposition to autoimmunity 5 .…”

“…The authors suggest that the association might be caused by subclinical systemic lupus erythematosus in three of them due to the presence of antinuclear antibodies, including both cases with recurrent dd, although this has been contested due to the fact that two of their patients could actually have NMo [16][17][18] . Kister et al 9 report on 4 patients that presented recurrent NMo years after undergoing thymectomy for MG. Two of these patients were positive for NMo-Ig antibodies in their serum 18 and ANA and anti-GAd were also present in 3 patients, disclosing systemic immune abnormalities. In both series, as in other cases reported before 7,[12][13][14][15] patients developed dd years after undergoing thymectomy, and the authors suggest that thymectomy might have induced immune dysregulation.…”

“…rarely, MG can be part of multiple autoimmune syndromes, including autoimmune diabetes mellitus, thrombotic thrombocytopenic purpura, sjögren syndrome, systemic lupus erythematosus, vitiligo, among other rare diseases 5 . In the past 20 years there has been an increasing number of reports on patients with MG presenting demyelinating diseases (dd) [6][7][8][9][10][11][12][13][14][15] , including multiple sclerosis, neuromyelitis optica (NMo), transverse myelitis and optic neuritis. however, it is not known whether this association is also part of unspecific immune activation, genetic susceptibility or if it just happens by random.…”

Current concepts in the diagnosis of transverse myelopathies

“…It is likely that these 8 8 patients have two coexisting autoimmune disorders rather than a vasculitic complication of a systemic autoimmune disease such as SLE or SS (35,36). Similarly, NMO may coexist with myasthenia gravis or other systemic autoimmune diseases (37,38) (Fig 8).…”