Anàlisi del títol d'anticossos anti-achr i la seva correlació clínica en pacients amb miastenia gravis seropositiva

Els anticossos contra el receptor de l'acetilcolina representen el principal mecanisme patogènic en la Miastènia Gravis, però la seva utilitat com a biomarcador durant el seguiment de la malaltia és desconeguda

Three-dimensional imaging in myotonic dystrophy type 1

Altres ajuts: The research of G. Nogales-Gadea, A. Ramos-Fransi, and A. Lucia is funded by Instituto de Salud Carlos III and cofinanced by Fondos FEDER. G. Nogales-Gadea is supported by a Miguel Servet research contract and by a Trampoline Grant #21108 from AFM Telethon. A. Ballester-Lopez is funded by an FI Agaur fellowship and Generalitat de Catalunya. E. Koehorst is funded by the La Caixa Foundation (ID 100010434), fellowship code LCF/BQ/IN18/11660019, cofunded by the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 713673. I. Linares-Pardo is funded by CP14/00032 and SGR 1520 (GRC) Generalitat de Catalunya. J. Núñez-Manchón was funded by AFM Telethon Trampoline Grant #21108. G. Lucente was supported by a Rio Hortega contract. J. Chojnacki is supported by European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant . The funding bodies had no role in the design of the study and collection, analysis, and interpretation of data.We aimed to determine whether 3D imaging reconstruction allows identifying molecular:clinical associations in myotonic dystrophy type 1 (DM1). We obtained myoblasts from 6 patients with DM1 and 6 controls. We measured cytosine-thymine-guanine (CTG) expansion and detected RNA foci and muscleblind like 1 (MBNL1) through 3D reconstruction. We studied dystrophia myotonica protein kinase (DMPK) expression and splicing alterations of MBNL1, insulin receptor, and sarcoplasmic reticulum Ca(2+)-ATPase 1. Three-dimensional analysis showed that RNA foci (nuclear and/or cytoplasmic) were present in 45%-100% of DM1-derived myoblasts we studied (range: 0-6 foci per cell). RNA foci represented <0.6% of the total myoblast nuclear volume. CTG expansion size was associated with the number of RNA foci per myoblast (r = 0.876 [95% confidence interval 0.222-0.986]) as well as with the number of cytoplasmic RNA foci (r = 0.943 [0.559-0.994]). Although MBNL1 colocalized with RNA foci in all DM1 myoblast cell lines, colocalization only accounted for 1% of total MBNL1 expression, with the absence of DM1 alternative splicing patterns. The number of RNA foci was associated with DMPK expression (r = 0.967 [0.079-0.999]). On the other hand, the number of cytoplasmic RNA foci was correlated with the age at disease onset (r = −0.818 [−0.979 to 0.019]). CTG expansion size modulates RNA foci number in myoblasts derived from patients with DM1. MBNL1 sequestration plays only a minor role in the pathobiology of the disease in these cells. Higher number of cytoplasmic RNA foci is related to an early onset of the disease, a finding that should be corroborated in future studies

The need for establishing a universal CTG sizing method in myotonic dystrophy type 1

The number of cytosine-thymine-guanine (CTG) repeats (‘CTG expansion size’) in the 3′untranslated region (UTR) region of the dystrophia myotonica-protein kinase (DMPK) gene is a hallmark of myotonic dystrophy type 1 (DM1), which has been related to age of disease onset and clinical severity. However, accurate determination of CTG expansion size is challenging due to its characteristic instability. We compared five different approaches (heat pulse extension polymerase chain reaction [PCR], long PCR-Southern blot [with three different primers sets—1, 2 and 3] and small pool [SP]-PCR) to estimate CTG expansion size in the progenitor allele as well as the most abundant CTG expansion size, in 15 patients with DM1. Our results indicated variability between the methods (although we found no overall differences between long PCR 1 and 2 and SP-PCR, respectively). While keeping in mind the limited sample size of our patient cohort, SP-PCR appeared as the most suitable technique, with an inverse significant correlation found between CTG expansion size of the progenitor allele, as determined by this method, and age of disease onset (r = −0.734, p = 0.016). Yet, in light of the variability of the results obtained with the different methods, we propose that an international agreement is needed to determine which is the most suitable method for assessing CTG expansion size in DM1

Drug-refractory myasthenia gravis : Clinical characteristics, treatments, and outcome

Altres ajuts: R. Alvarez-Velasco was supported by grant SLT008/18/00207 from the Health Research and Innovation Strategic Plan (PERIS). The NMD-ES Project and F. PlaJunca (data curator) are partially funded by the Centro de Investigacion Biomédica en Red de Enfermedades Raras (CIBERER).To describe the clinical characteristics and outcomes in patients with refractory myasthenia gravis (MG) and to determine the effectiveness and side effects of the drugs used for their treatment. This observational retrospective cross-sectional multicenter study was based on data from the Spanish MG Registry (NMD-ES). Patients were considered refractory when their MG Foundation of America post-interventional status (MGFA-PIS) was unchanged or worse after corticosteroids and two or more other immunosuppressive agents. Clinical and immunologic characteristics of drug-refractory patients, efficiency and toxicity of drugs used, and outcome (MGFA-PIS) at end of follow-up were studied. We included 990 patients from 15 hospitals. Eighty-four patients (68 of 842 anti-acetylcholine receptor [AChR], 5 of 26 anti-muscle-specific tyrosine kinase [MusK], 10 of 120 seronegative, and 1 of 2 double-seropositive patients) were drug refractory. Drug-refractory patients were more frequently women (p < 0.0001), younger at onset (p < 0.0001), and anti-MuSK positive (p = 0.037). Moreover, they more frequently presented a generalized form of the disease, bulbar symptoms, and life-threatening events (p < 0.0001; p = 0.018; and p = 0.002, respectively) than non-drug-refractory patients. Mean follow-up was 9.8 years (SD 4.5). Twenty-four (50%) refractory patients had side effects to one or more of the drugs. At the end of follow-up, 42.9% of drug-refractory patients (42.6% of anti-AChR, 100% of anti-MuSK, and 10% of seronegative patients) and 79.8% of non-drug-refractory patients (p < 0.0001) achieved remission or had minimal manifestations. Eighty percent of drug-refractory-seronegative patients did not respond to any drug tested. In this study, 8.5% of MG patients were drug-refractory. New more specific drugs are needed to treat drug-refractory MG patients

Preliminary findings on CTG expansion determination in different tissues from patients with myotonic dystrophy type 1

Myotonic Dystrophy type 1 (DM1) is characterized by a high genetic and clinical variability. Determination of the genetic variability in DM1 might help to determine whether there is an association between CTG (Cytosine-Thymine-Guanine) expansion and the clinical manifestations of this condition. We studied the variability of the CTG expansion (progenitor, mode, and longest allele, respectively, and genetic instability) in three tissues (blood, muscle, and tissue) from eight patients with DM1. We also studied the association of genetic data with the patients’ clinical characteristics. Although genetic instability was confirmed in all the tissues that we studied, our results suggest that CTG expansion is larger in muscle and skin cells compared with peripheral blood leukocytes. While keeping in mind that more research is needed in larger cohorts, we have provided preliminary evidence suggesting that the estimated progenitor CTG size in muscle could be potentially used as an indicator of age of disease onset and muscle function impairment

Clinical characteristics and outcomes of thymoma-associated myasthenia gravis

[Background and purpose] Prognosis of myasthenia gravis (MG) in patients with thymoma is not well established. Moreover, it is not clear whether thymoma recurrence or unresectable lesions entail a worse prognosis of MG.[Methods] This multicenter study was based on data from a Spanish neurologist-driven MG registry. All patients were aged >18 years at onset and had anti-acetylcholine receptor antibodies. We compared the clinical data of thymomatous and nonthymomatous patients. Prognosis of patients with recurrent or nonresectable thymomas was assessed.[Results] We included 964 patients from 15 hospitals; 148 (15.4%) had thymoma-associated MG. Median follow-up time was 4.6 years. At onset, thymoma-associated MG patients were younger (52.0 vs. 60.4 years, p < 0.001), had more generalized symptoms (odds ratio [OR]: 3.02, 95% confidence interval [CI]: 1.95–4.68, p < 0.001) and more severe clinical forms according to the Myasthenia Gravis Foundation of America (MGFA) scale (OR: 1.6, 95% CI: 1.15–2.21, p = 0.005). Disease severity based on MGFA postintervention status (MGFA-PIS) was higher in thymomatous patients at 1 year, 5 years, and the end of follow-up. Treatment refractoriness and mortality were also higher (OR: 2.28, 95% CI: 1.43–3.63, p = 0.001; hazard ratio: 2.46, 95% CI: 1.47–4.14, p = 0.001). Myasthenic symptoms worsened in 13 of 27 patients with recurrences, but differences in long-term severity were not significant. Fifteen thymomatous patients had nonresectable thymomas with worse MGFA-PIS and higher mortality at the end of follow-up.[Conclusions] Thymoma-associated MG patients had more severe myasthenic symptoms and worse prognosis. Thymoma recurrence was frequently associated with transient worsening of MG, but long-term prognosis did not differ from nonrecurrent thymoma. Patients with nonresectable thymoma tended to present severe forms of MG.This work is supported by Fondo de Investigaciones Sanitarias (FIS) grant FIS19/01774, Instituto de Salud Carlos III and cofunded by the European Union (ERDF/ESF, A Way to Make Europe/Investing in Your Future). Rodrigo Álvarez-Velasco was supported by a PhD for Medical Doctors grant from the Pla Estratègic de Recerca i Innovació en Salut (PERIS), Generalitat de Catalunya (SLT008/18/00207). Elena Cortés-Vicente was supported by a Juan Rodés grant (JR19/00037) from the Fondo de Investigación en Salud, Instituto de Salud Carlos III, Ministry of Health (Spain).Peer reviewe

A DM1 family with interruptions associated with atypical symptoms and late onset but not with a milder phenotype

Carriage of interruptions in CTG repeats of the myotonic dystrophy protein kinase gene has been associated with a broad spectrum of myotonic dystrophy type 1 (DM1) phenotypes, mostly mild. However, the data available on interrupted DM1 patients and their phenotype are scarce. We studied 49 Spanish DM1 patients, whose clinical phenotype was evaluated in depth. Blood DNA was obtained and analyzed through triplet‐primed polymerase chain reaction (PCR), long PCR‐Southern blot, small pool PCR, AciI digestion, and sequencing. Five patients of our registry (10%), belonging to the same family, carried CCG interruptions at the 3’ end of the CTG expansion. Some of them presented atypical traits such as a very late onset of symptoms (&gt;50 years) and a severe axial and proximal weakness requiring walking assistance. They also showed classic DM1 symptoms including cardiac and respiratory dysfunction, which were severe in some of them. Sizes and interrupted allele patterns were determined, and we found a contraction and an expansion in two intergenerational transmissions. Our study contributes to the observation that DM1 patients carrying interruptions present with atypical clinical features that can make DM1 diagnosis difficult, with a later than expected age of onset and a previously unreported aging‐related severe disease manifestation

Anàlisi del títol d’anticossos anti-achr i la seva correlació clínica en pacients amb miastenia gravis seropositiva

Els anticossos contra el receptor de l’acetilcolina representen el principal mecanisme patogènic en la Miastènia Gravis, però la seva utilitat com a biomarcador durant el seguiment de la malaltia és desconeguda. S’ha realitzat un estudi retrospectiu amb 77 pacients que disposen de múltiples determinacions en el títol d’anticossos, relacionant-los amb l’estat clínic de cada moment. L’anàlisi demostra una correlació significativa entre la variació dels Ac i l’evolució clínica intrapacient, tant al llarg de la malaltia com en les fluctuacions clíniques. Per tant, la determinació seriada d’anticossos representa una mida dels canvis clínics i pot ser d’utilitat en el seguiment d’aquests pacients

Nuevos biomarcadores diagnósticos y factores pronósticos en la miastenia gravis

La Miastenia Gravis (MG) es una enfermedad autoinmune en la que los anticuerpos reconocen proteínas de la postsinapsis neuromuscular (Receptor Acetilcolina, MuSK, LRP4, Cortactin). Clínicamente, los pacientes presentan fatigabilidad que puede ser ocular o generalizada. En las formas generalizadas puede existir afectación de la musculatura bulbar, que en ocasiones es grave y comporta una situación de riesgo vital para el paciente (SRV). Es una enfermedad heterogénea, por lo que el uso de biomarcadores es esencial para confirmar el diagnóstico preciso y garantizar un abordaje óptimo del paciente, especialmente en las SRV. Actualmente, los biomarcadores diagnósticos útiles en la MG son los diferentes autoanticuerpos y los estudios electrofisiológicos. Los anticuerpos antiMUSK son los únicos biomarcadores con correlación clínica en el reducido subgrupo de pacientes con MG y estos autoanticuerpos. Hasta el momento, no se han identificado marcadores clínicos ni serológicos capaces de determinar el riesgo de padecer una SRV, ni de predecir la evolución de ésta o la respuesta a las diferentes terapias. El primer objetivo de esta tesis fue estudiar el papel de los miRNAs circulantes como nuevos biomarcadores en la MG. El segundo objetivo fue estudiar si existía algún marcador pronóstico en pacientes con MG que presentaban una SRV. Los miRNAs son pequeñas moléculas no codificantes implicadas en la regulación de un gran número de genes, y que se han propuesto como biomarcadores en un gran número de enfermedades. En la MG se había descrito el perfil de miRNAs en células mononucleares de sangre periférica, pero el perfil de miRNAs circulantes no se había estudiado. Analizamos el perfil de miRNAs circulantes mediante qPCR. Siete miRNAs mostraron niveles inferiores en los pacientes con MG comparados con los controles. El miR15b se encontró en niveles más bajos en los 3 grupos de pacientes (Early onset MG -EoMG-, Late onset MG -LoMG- y MG con timoma). El miR122, miR140-3p, miR-185, miR-192 y miR20b se encontraron bajos en los EoMG y LoMG. El miR885-5p mostró niveles bajos sólo en LoMG. Puesto que EoMG y LoMG presentaban un perfil común de miRNAs esto sugiere que, al menos en parte, comparten un mismo mecanismo fisiopatológico. El perfil de miRNAs en los pacientes con timoma inesperadamente no mostraba diferencias respecto al resto de subgrupos, así como tampoco se detectaron diferencias en función del tratamiento recibido. Como conclusión, el estudio de los miRNAs circulantes en pacientes con MG puede aportar nueva información sobre la patogenia de esta enfermedad, aunque su utilidad como biomarcadores clínicos debe aún ser establecida. Para identificar los posibles factores capaces de determinar el riesgo de padecer una SRV o de predecir la evolución de ésta, realizamos un estudio retrospectivo de los pacientes incluidos en el registro nacional de enfermedades neuromusculares (NMD-ES) que habían presentado alguna SRV. De los 648 pacientes con una forma generalizada de MG incluidos en el registro, 62 (9’56%) tuvieron una SRV y 29/62 (4’47%) se encontraban bajo tratamiento inmunosupresor. 32 estaban en estadio MGFA V al requerir soporte ventilatorio, y 30 en estadio IVB al necesitar una SNG para alimentación. No se detectó ningún factor de riesgo significativo para presentar una SRV. El desencadenante más frecuente fueron las infecciones, pero no implicaban un peor pronóstico. La mediana de tiempo hasta la retirada de la SNG fue de 13 días (1-434) y la de extubación fue de 12 días (3-176) y fue significativamente menor en los LoMG, demostrando que la edad tampoco implicaba un peor pronóstico. Cuatro pacientes fallecieron, todos LoMG con múltiples comorbilidades. El 20% de pacientes persistían en SRV al cabo de un mes. Por tanto, aunque el porcentaje de SRV en pacientes afectos de MG es bajo, existe aún un subgrupo de pacientes que presentan SRV prolongadas, lo que resalta la necesidad de nuevas terapias más rápidas y efectivas para estos casos.Myasthenia Gravis (MG) is an autoimmune disease with antibodies against postsynaptic proteins in the neuromuscular junction (Acetilcholine receptor, MuSK, LRP4, Cortactin). From the clinical point of view, patients with MG present ocular or generalized fatigability. When there is bulbar involvement, weakness can be severe and at times life-threatening. It is a highly heterogeneous disease, and therefore the use of biomarkers is essential to confirm the diagnosis and guarantee an optimal achievement to patients, especially in life-threatening events (LTE). Nowadays, the only diagnostic biomarkers in MG are the different autoantibodies and the electrophysiological tests, and antiMUSK antibodies are the only biomarkers with clinical correlation in a small subgroup of patients. Besides, no consistent prognostic factors have been identified to predict the risk to present a life-threatening event (LTE) or to predict their evolution and response to treatment. The first objective of this thesis was to describe the profile of circulating miRNAs in serum of patients with MG and their utility as biomarkers. The second objective was to evaluate the prognostic factors of MG patients who presented an LTE. MiRNAs are small non-coding molecules involved in the regulation of a large amount of genes, and have been proposed as biomarkers in different diseases. The profile of miRNAs has been previously described in peripheral blood mononuclear cells of patients with MG, but not in serum. An analysis of circulating miRNAs in patients with MG and AChR antibodies was performed by qPCR, and a different expression of 7 miRNAs was found. MiR15b was found in lower levels in the 3 groups of patients (Early onset MG -EoMG-, Late onset MG -LoMG- and MG with thymoma). MiR122, miR140-3p, miR185, miR192 and miR20b were found in lower levels in EoMG and LoMG. MiR885-5p was found in lower levels only in LoMG. As EoMG and LoMG share a miRNA profile, this supports that they probably share a common altered mechanism. Patients with thymoma did not express a characteristic profile of circulating miRNAs, and there was no difference either in the serum miRNA profile depending on the treatment. Our results demonstrate that the analysis of circulating miRNAs can provide useful information about pathogenic mechanisms in MG. To identify the risk factors to present a LTE, or to predict their evolution and response to treatment, a survey was performed of patients with MG included in a nationwide registry in Spain (NMD-ES). From the total of 648 patients included, 62 (9’56%) presented a LTE and 29/62 (4’47% of 648) were under immunosuppressant treatment. Thirty-two had a MGFA V status and required intubation, and 30 were in IVB status and needed a feeding tube. There was not any identifiable risk factor to predict the LTE. The most frequent precipitating factor was infections, but it did not imply a worse outcome. Median time to removal of the feeding tube was 13 days (1-434). Median time to weaning was 12 days (3-176), and it was shorter in LoMG than in EoMG. Thus, age did neither imply a worse outcome. Four patients died, all of them with LoMG and severe comorbidities. Twenty per cent of patients remained in a life-threatening situation after one month. Therefore, it is important to find new biomarkers to identify these resistant patients and to improve our therapeutic arsenal with more efficacious and faster drugs

Nuevos biomarcadores diagnósticos y factores pronósticos en la miastenia gravis

La Miastenia Gravis (MG) es una enfermedad autoinmune en la que los anticuerpos reconocen proteínas de la postsinapsis neuromuscular (Receptor Acetilcolina, MuSK, LRP4, Cortactin). Clínicamente, los pacientes presentan fatigabilidad que puede ser ocular o generalizada. En las formas generalizadas puede existir afectación de la musculatura bulbar, que en ocasiones es grave y comporta una situación de riesgo vital para el paciente (SRV). Es una enfermedad heterogénea, por lo que el uso de biomarcadores es esencial para confirmar el diagnóstico preciso y garantizar un abordaje óptimo del paciente, especialmente en las SRV. Actualmente, los biomarcadores diagnósticos útiles en la MG son los diferentes autoanticuerpos y los estudios electrofisiológicos. Los anticuerpos antiMUSK son los únicos biomarcadores con correlación clínica en el reducido subgrupo de pacientes con MG y estos autoanticuerpos. Hasta el momento, no se han identificado marcadores clínicos ni serológicos capaces de determinar el riesgo de padecer una SRV, ni de predecir la evolución de ésta o la respuesta a las diferentes terapias. El primer objetivo de esta tesis fue estudiar el papel de los miRNAs circulantes como nuevos biomarcadores en la MG. El segundo objetivo fue estudiar si existía algún marcador pronóstico en pacientes con MG que presentaban una SRV. Los miRNAs son pequeñas moléculas no codificantes implicadas en la regulación de un gran número de genes, y que se han propuesto como biomarcadores en un gran número de enfermedades. En la MG se había descrito el perfil de miRNAs en células mononucleares de sangre periférica, pero el perfil de miRNAs circulantes no se había estudiado. Analizamos el perfil de miRNAs circulantes mediante qPCR. Siete miRNAs mostraron niveles inferiores en los pacientes con MG comparados con los controles. El miR15b se encontró en niveles más bajos en los 3 grupos de pacientes (Early onset MG -EoMG-, Late onset MG -LoMG- y MG con timoma). El miR122, miR140-3p, miR-185, miR-192 y miR20b se encontraron bajos en los EoMG y LoMG. El miR885-5p mostró niveles bajos sólo en LoMG. Puesto que EoMG y LoMG presentaban un perfil común de miRNAs esto sugiere que, al menos en parte, comparten un mismo mecanismo fisiopatológico. El perfil de miRNAs en los pacientes con timoma inesperadamente no mostraba diferencias respecto al resto de subgrupos, así como tampoco se detectaron diferencias en función del tratamiento recibido. Como conclusión, el estudio de los miRNAs circulantes en pacientes con MG puede aportar nueva información sobre la patogenia de esta enfermedad, aunque su utilidad como biomarcadores clínicos debe aún ser establecida. Para identificar los posibles factores capaces de determinar el riesgo de padecer una SRV o de predecir la evolución de ésta, realizamos un estudio retrospectivo de los pacientes incluidos en el registro nacional de enfermedades neuromusculares (NMD-ES) que habían presentado alguna SRV. De los 648 pacientes con una forma generalizada de MG incluidos en el registro, 62 (9’56%) tuvieron una SRV y 29/62 (4’47%) se encontraban bajo tratamiento inmunosupresor. 32 estaban en estadio MGFA V al requerir soporte ventilatorio, y 30 en estadio IVB al necesitar una SNG para alimentación. No se detectó ningún factor de riesgo significativo para presentar una SRV. El desencadenante más frecuente fueron las infecciones, pero no implicaban un peor pronóstico. La mediana de tiempo hasta la retirada de la SNG fue de 13 días (1-434) y la de extubación fue de 12 días (3-176) y fue significativamente menor en los LoMG, demostrando que la edad tampoco implicaba un peor pronóstico. Cuatro pacientes fallecieron, todos LoMG con múltiples comorbilidades. El 20% de pacientes persistían en SRV al cabo de un mes. Por tanto, aunque el porcentaje de SRV en pacientes afectos de MG es bajo, existe aún un subgrupo de pacientes que presentan SRV prolongadas, lo que resalta la necesidad de nuevas terapias más rápidas y efectivas para estos casos.Myasthenia Gravis (MG) is an autoimmune disease with antibodies against postsynaptic proteins in the neuromuscular junction (Acetilcholine receptor, MuSK, LRP4, Cortactin). From the clinical point of view, patients with MG present ocular or generalized fatigability. When there is bulbar involvement, weakness can be severe and at times life-threatening. It is a highly heterogeneous disease, and therefore the use of biomarkers is essential to confirm the diagnosis and guarantee an optimal achievement to patients, especially in life-threatening events (LTE). Nowadays, the only diagnostic biomarkers in MG are the different autoantibodies and the electrophysiological tests, and antiMUSK antibodies are the only biomarkers with clinical correlation in a small subgroup of patients. Besides, no consistent prognostic factors have been identified to predict the risk to present a life-threatening event (LTE) or to predict their evolution and response to treatment. The first objective of this thesis was to describe the profile of circulating miRNAs in serum of patients with MG and their utility as biomarkers. The second objective was to evaluate the prognostic factors of MG patients who presented an LTE. MiRNAs are small non-coding molecules involved in the regulation of a large amount of genes, and have been proposed as biomarkers in different diseases. The profile of miRNAs has been previously described in peripheral blood mononuclear cells of patients with MG, but not in serum. An analysis of circulating miRNAs in patients with MG and AChR antibodies was performed by qPCR, and a different expression of 7 miRNAs was found. MiR15b was found in lower levels in the 3 groups of patients (Early onset MG -EoMG-, Late onset MG -LoMG- and MG with thymoma). MiR122, miR140-3p, miR185, miR192 and miR20b were found in lower levels in EoMG and LoMG. MiR885-5p was found in lower levels only in LoMG. As EoMG and LoMG share a miRNA profile, this supports that they probably share a common altered mechanism. Patients with thymoma did not express a characteristic profile of circulating miRNAs, and there was no difference either in the serum miRNA profile depending on the treatment. Our results demonstrate that the analysis of circulating miRNAs can provide useful information about pathogenic mechanisms in MG. To identify the risk factors to present a LTE, or to predict their evolution and response to treatment, a survey was performed of patients with MG included in a nationwide registry in Spain (NMD-ES). From the total of 648 patients included, 62 (9’56%) presented a LTE and 29/62 (4’47% of 648) were under immunosuppressant treatment. Thirty-two had a MGFA V status and required intubation, and 30 were in IVB status and needed a feeding tube. There was not any identifiable risk factor to predict the LTE. The most frequent precipitating factor was infections, but it did not imply a worse outcome. Median time to removal of the feeding tube was 13 days (1-434). Median time to weaning was 12 days (3-176), and it was shorter in LoMG than in EoMG. Thus, age did neither imply a worse outcome. Four patients died, all of them with LoMG and severe comorbidities. Twenty per cent of patients remained in a life-threatening situation after one month. Therefore, it is important to find new biomarkers to identify these resistant patients and to improve our therapeutic arsenal with more efficacious and faster drugs