Anti-Neuronal IgG4 Autoimmune Diseases and IgG4-Related Diseases May Not Be Part of the Same Spectrum: A Comparative Study.

Background: IgG4 is associated with two emerging groups of rare diseases: 1) IgG4 autoimmune diseases (IgG4-AID) and 2) IgG4-related diseases (IgG4-RLD). Anti-neuronal IgG4-AID include MuSK myasthenia gravis, LGI1- and Caspr2-encephalitis and autoimmune nodo-/paranodopathies (CNTN1/Caspr1 or NF155 antibodies). IgG4-RLD is a multiorgan disease hallmarked by tissue-destructive fibrotic lesions with lymphocyte and IgG4 plasma cell infiltrates and increased serum IgG4 concentrations. It is unclear whether IgG4-AID and IgG4-RLD share relevant clinical and immunopathological features. Methods: We collected and analyzed clinical, serological, and histopathological data in 50 patients with anti-neuronal IgG4-AID and 19 patients with IgG4-RLD. Results: A significantly higher proportion of IgG4-RLD patients had serum IgG4 elevation when compared to IgG4-AID patients (52.63% vs. 16%, p = .004). Moreover, those IgG4-AID patients with elevated IgG4 did not meet the diagnostic criteria of IgG4-RLD, and their autoantibody titers did not correlate with their serum IgG4 concentrations. In addition, patients with IgG4-RLD were negative for anti-neuronal/neuromuscular autoantibodies and among these patients, men showed a significantly higher propensity for IgG4 elevation, when compared to women (p = .005). Last, a kidney biopsy from a patient with autoimmune paranodopathy due to CNTN1/Caspr1-complex IgG4 autoantibodies and concomitant nephrotic syndrome did not show fibrosis or IgG4+ plasma cells, which are diagnostic hallmarks of IgG4-RLD. Conclusion: Our observations suggest that anti-neuronal IgG4-AID and IgG4-RLD are most likely distinct disease entities.

Status epilepticus admissions during the COVID-19 pandemic in Salzburg-A population-based study.

Several emergencies were admitted less frequently to the hospital during the coronavirus disease 2019 (COVID-19) pandemic. To investigate whether this also occurred with status epilepticus (SE) we compared admissions due to first SE from March to April 2020 ("Time of COVID," TOC) with January to February 2020 ("pre-COVID," preCOV). We also compared admission numbers in TOC and preCOV with the respective 2-month periods in 2018 and 2019 in a retrospective cohort analysis. Two investigators independently searched the hospital patient database for various forms of SE. There was no significant change in the 2-month incidences of first SE in the city of Salzburg from preCOV of 6.1 (95% confidence interval [CI] 2.9-12.3) to TOC of 6.9/100 000 adults (95% CI 3.4-13.3). Admission numbers did not differ significantly from previous years. Estimated adjusted incidence was in line with a recent 5-year epidemiological study in Salzburg. However, a trend toward less-frequent nonconvulsive SE (NCSE) and loss of female predominance were indirect hints of underdiagnosing SE. In contrast to other medical conditions, SE most often presents clinically with impaired consciousness, which may promote admission to emergency departments even in times of lock-down. Further research of medical support of women and patients with NCSE during pandemic-related restrictions is warranted.