Demyelinating disease in patients with myasthenia gravis

Abstract

-Myasthenia gravis (MG) is an autoimmune disease characterized by fluctuating muscle weakness, caused by impaired neuromuscular transmission. Patients with MG can present other autoimmune diseases in association, commonly hypo or hyperthyroidism. The association of MG to demyelinating disease is rare and has been described before. We report on three Brazilian patients with MG that presented distinct demyelinating diseases, two monophasic and one recurrent neuromyelitis optica, several years after the diagnosis of MG, and discuss their clinical courses.Key Words: myasthenia gravis, demyelinating disease, association. Doenças desmielinizantes em pacientes com miastenia gravisResumo -Miastenia gravis (MG) é doença autoimune caracterizada por episódios de fraqueza muscular alternados com melhora, causada por bloqueio da junção neuromuscular. Pacientes com MG podem apresentar outras doenças autoimunes, comumente hipo ou hipertiroidismo, e a associação de MG com doenças desmielinizantes é raramente descrita. relatamos três pacientes brasileiros com MG que desenvolveram doenças desmielinizantes, dois monofásicos e um neuromielite óptica recorrente, vários anos após o diagnóstico de MG e discutimos seus cursos clínicos.PAlAvrAs-chAve: miastenia gravis, doenças desmielinizante, associação. Myasthenia gravis (MG) is an autoimmune disease characterized by fluctuating muscle weakness, caused by impaired neuromuscular transmission. Autoantibodies specific for the human nicotinic acetylcholine receptor are present in 70 to 80% of the patients, and the remaining cases can be associated with antibodies targeted at muscle specific kinase (MusK) and other proteins in the post-synaptic membrane 1,2 . MG has a bimodal incidence: (1) 20 to 40 years-old, predominated by women, and (2) 60 to 80 years-old, predominated by men 2 .Patients with MG commonly have thyroid disease and can present with nonspecific immune system abnormalities, such as positive auto antibodies and alopecia areata 3-5 . 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) 6-15 , 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.We herein describe three Brazilian patients with MG that presented different dd and discuss their clinical courses. methoDWe reviewed the records of 630 patients followed for MG at the Neuroimmunology clinic of the Federal University of sao Paulo between 1979 and 2006. The diagnosis of MG was based on clinical history, neurological examination, electrophysiological testing and response to acetyl cholinesterase inhibitor medication (pyridostigmi...

NMO-IgG positive neuromyelitis optica in a patient with myasthenia gravis but no thymectomy

“…Clinical and serological findings of concomitant autoimmunity have been described in as many as 50% of NMO patients and up to 25% of MG patients, but coexistence of both conditions, as seen in our patient, is rare with only 12 cases documented in the English literature [3][4][5][6][7][8][9][10][11][13][14][15][16][17][18].…”

“…Accordingly, these brain lesions have identical histopathological features to those found in the spinal cord and optic nerve [2]. MG patients can rarely present brain abnormalities, but brain lesions in patients with MG associated with NMO have been documented only in one case thus far; that patient had few scattered subcortical foci of increased T2 signal intensity without gadolinium enhancement, which were unchanged after several years of follow-up, while our patient had progressive demyelinating brain lesions [4][5][6][7]11,[14][15][16][17].…”

“…This highly specific antibody is present in about 80% of MG patients, and the remaining cases are associated with antibodies targeting other proteins in the postsynaptic membrane [1,11]. Recently, the presence of serum autoantibodies against the aquaporin-4 (AQP-4) water channel in patients with NMO, named NMO-IgG, demonstrated the autoimmune nature of this disease [12,19,20].…”

“…In all cases reported thus far, NMO followed thymectomy for MG, suggesting that thymectomy might be a prerequisite for the development of NMO in patients with MG [3][4][5][6][7][8]. NMO-IgG antibodies were not determined in most cases [3,4,6,10,11].…”

“…Coexistence of MG and NMO has only rarely been documented [3][4][5][6][7][8][9][10][11]. In all cases reported thus far, NMO followed thymectomy for MG, suggesting that thymectomy might be a prerequisite for the development of NMO in patients with MG [3][4][5][6][7][8].…”