Late Onset Myasthenia Gravis Is Associated with HLA DRB1*15:01 in the Norwegian Population

BACKGROUND: Acquired myasthenia gravis (MG) is a rare antibody-mediated autoimmune disease caused by impaired neuromuscular transmission, leading to abnormal muscle fatigability. The aetiology is complex, including genetic risk factors of the human leukocyte antigen (HLA) complex and unknown environmental factors. Although associations between the HLA complex and MG are well established, not all involved components of the HLA predisposition to this heterogeneous disease have been revealed. Well-powered and comprehensive HLA analyses of subgroups in MG are warranted, especially in late onset MG. METHODOLOGY/PRINCIPAL FINDINGS: This case-control association study is of a large population-based Norwegian cohort of 369 MG patients and 651 healthy controls. We performed comprehensive genotyping of four classical HLA loci (HLA-A, -B, -C and -DRB1) and showed that the DRB1*15:01 allele conferred the strongest risk in late onset MG (LOMG; onset ≥ 60 years) (OR 2.38, p(c)7.4 × 10(-5)). DRB1*13:01 was found to be a protective allele for both early onset MG (EOMG) and LOMG (OR 0.31, p(c) 4.71 × 10(-4)), a finding not previously described. No significant association was found to the DRB1*07:01 allele (p(nc) = 0.18) in a subset of nonthymomatous anti-titin antibody positive LOMG as reported by others. HLA-B*08 was mapped to give the strongest contribution to EOMG, supporting previous studies. CONCLUSION: The results from this study provide important new information concerning the susceptibility of HLA alleles in Caucasian MG, with highlights on DRB1*15:01 as being a major risk allele in LOMG

EFNS/ENS Guidelines for the treatment of ocular myasthenia.

BACKGROUND AND PURPOSE: The symptoms of acquired autoimmune ocular myasthenia are restricted to the extrinsic eye muscles, causing double vision and drooping eyelids. These guidelines are designed to provide advice about best clinical practice based on the current state of clinical and scientific knowledge and the consensus of an expert panel. SEARCH STRATEGY: Evidence for these guidelines was collected by searches in the MEDLINE and Cochrane databases. The task force working group reviewed evidence from original articles and systematic reviews. The evidence was classified (I, II, III, IV) and consensus recommendation graded (A, B or C) according to the EFNS guidance. Where there was a lack of evidence but clear consensus, good practice points are provided. CONCLUSIONS: The treatment of ocular myasthenia should initially be started with pyridostigmine (good practice point). If this is not successful in relieving symptoms, oral corticosteroids should be used on an alternate-day regimen (recommendation level C). If steroid treatment does not result in good control of the symptoms or if it is necessary to use high steroid doses, steroid-sparing treatment with azathioprine should be started (recommendation level C). If ocular myasthenia gravis is associated with thymoma, thymectomy is indicated. Otherwise, the role of thymectomy in ocular myasthenia is controversial. Steroids and thymectomy may modify the course of ocular myasthenia and prevent myasthenia gravis generalization (good practice point)

Juvenile myasthenia gravis in Norway: HLA-DRB1*04:04 is positively associated with prepubertal onset

<div><p>Background</p><p>Juvenile myasthenia gravis (MG) is a rare autoantibody mediated autoimmune disorder targeting the neuromuscular endplate. The clinical hallmark is muscle weakness and fatigability. Disease aetiology is complex, including both genetic and environmental factors. The involvement of genes in the human leukocyte antigen (HLA) is well established in adult MG. However, HLA associations in European juvenile MG have not been studied. This case-control study aimed to investigate and characterize genetic risk factors in prepubertal and postpubertal onset juvenile MG.</p><p>Methodology/Principal findings</p><p>A population based Norwegian cohort of 43 juvenile MG patients (17 with prepubertal onset, 26 with postpubertal onset) and 368 controls were included. Next generation sequencing of five HLA loci (HLA-A, -B, -C, -DRB1 and -DQB1) was performed, and a positive association was seen with HLA-B*08 (OR (95% CI) = 3.27 (2.00–5.36), P_c = 0.00003) and HLA-DRB1*04:04 (OR (95% CI) = 2.65 (1.57–4.24), P_c = 0.03). Stratified in postpubertal and prepubertal onset, HLA-DRB1*04:04 was only positively associated with the latter (P = 0.01). The HLA-B*08 allele (12.9% in the controls), previously described associated with early onset adult MG, was most frequently observed in postpubertal onset MG (40.4%, P = 0.0002) but also increased among prepubertal onset MG (23.5%, P = 0.05).</p><p>Conclusion</p><p>This study provides novel information about HLA susceptibility alleles in Norwegian juvenile MG where HLA-DRB1*04:04 was associated with prepubertal onset.</p></div

Clinical characteristic of the Norwegian juvenile myasthenia gravis cohort stratified by age at onset.

<p>Clinical characteristic of the Norwegian juvenile myasthenia gravis cohort stratified by age at onset.</p

HLA alleles showing association (P_nc<0.05) with juvenile myasthenia gravis (JMG).

<p>HLA alleles showing association (P_nc<0.05) with juvenile myasthenia gravis (JMG).</p