Geographical Distribution of Myasthenia Gravis in Northern Europe--Results from a Population-Based Study from Two Countries.

OBJECTIVES: To compare the prevalence of myasthenia gravis (MG) subgroups based on immunological markers and clinical presentation in two geographically complete MG populations in northern Europe. METHODS: This cross-sectional study included all living MG patients in Norway and a regional cohort from the Netherlands. Patients were identified using their hospital registration codes. Medical charts of subjects >16 years were reviewed. Inclusion criteria were clinical MG, a positive antibody test for acetylcholine receptor (AChR MG) or muscle-specific kinase (MuSK MG), or if seronegative MG, confirmed by an electrophysiological test. RESULTS: 1,205 MG patients (534 Norwegians and 671 Dutch) fulfilled the criteria, giving a higher point prevalence in the Netherlands (167/million, 95% CI 155-180) than in Norway (138/million, 95% CI 126-150). In particular, rates of AChR MG (143 vs. 111/million), MuSK MG (6.5 vs. 0.5/million), and ocular phenotype (62 vs. 24/million) were higher in the Netherlands. CONCLUSION: Novel findings are an AChR MG geographical north-south gradient and a 2.6-fold more ocular MG patients in the Netherlands than in Norway. The MuSK MG latitudinal gradient supports the notion of a north-south gradient in Europe, with a higher prevalence in the south. The variation is probably explained by genetic differences between the populations, in addition to environmental interactions.

An up-date on health-related quality of life in myasthenia gravis -results from population based cohorts.

UNLABELLED: Current available therapies control Myasthenia gravis (MG) reasonably well, but Health Related Quality of life (HRQOL) remains lower than expected. The aim was provide insights in how HRQOL in MG stands across borders and time, compare the scores to general population controls and other chronic disorders and assess the impact of potential predictors for quality of life such as a) clinical characteristics b) antibodies c) thymoma and d) treatment in a population-based cohort. METHODS: We designed a population-based cross-sectional study including 858 patients, 373 from Norway and 485 from the Netherlands. The Short Form Health Survey 36 (SF-36) and a cross-cultural validated questionnaire were used. Data were in addition compared to the general population, other chronic diseases and previous studies. RESULTS: Mean physical composite score was 59.4 and mental composite score 69.0 with no differences between the countries. The mean HRQOL score was lower in patients with bulbar and generalized symptoms (p < 0.001) compared to sex and age adjusted healthy controls, but not in patients with ocular symptoms or patients in remission. Multivariate analysis revealed that female gender, generalized symptoms and use of secondary immunosuppressive drugs at the time of testing were risk factors for reduced HRQOL. CONCLUSIONS: Remission and absence of generalized symptoms were favorable factors for HRQOL in MG patients. Historically, the HRQOL levels have not changed since 2001 and no new clinical predictors could be detected in this exhaustive population-based study. Further studies should explore the impact of non clinical factors like ethnic variations, socio-economic and hormonal factors on HRQOL.

Pathogenic immune mechanisms at the neuromuscular synapse: the role of specific antibody-binding epitopes in myasthenia gravis.

Autoantibodies against three different postsynaptic antigens and one presynaptic antigen at the neuromuscular junction are known to cause myasthenic syndromes. The mechanisms by which these antibodies cause muscle weakness vary from antigenic modulation and complement-mediated membrane damage to inhibition of endogenous ligand binding and blocking of essential protein-protein interactions. These mechanisms are related to the autoantibody titre, specific epitopes on the target proteins and IgG autoantibody subclass. We here review the role of specific autoantibody-binding epitopes in myasthenia gravis, their possible relevance to the pathophysiology of the disease and potential implications of epitope mapping knowledge for new therapeutic strategies.

Lambert-Eaton myasthenic syndrome in a 13-year-old girl with Xp11.22-p11.23 duplication.

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease of the presynaptic neuromuscular junction, typically occurring in adults as a paraneoplastic syndrome. Only rare cases have been reported in childhood. In most childhood cases, malignancies have not been detected but a propensity to autoimmune disease was noticed. Nevertheless, little is known about genetic factors that may contribute to the susceptibility of an individual to develop LEMS. We report on a 13-year-old girl, known with the Xp11.22-p11.23 duplication syndrome, who presented with severe non-paraneoplastic LEMS. The potential role of this microduplication syndrome in the development of LEMS is explored. Previous literature review of twelve Xp11.2 duplication syndrome patients showed that three of them suffered from various autoimmune diseases. The common duplicated region in those three patients and the presented case comprises 12 disease-associated genes including the FOXP3 (Forkhead Box P3) and WAS (Wiskott-Aldrich syndrome) gene, both implicated in immune function. However, it is unclear whether increased gene dosage of one or both of these genes can cause susceptibility to autoimmune diseases. In conclusion, the presented case emphasizes that autoimmune disease is a recurrent feature of the Xp11.2 duplication syndrome, which should be considered in the follow-up of these patients. The exact mechanism underlying this autoimmune propensity remains to be elucidated.