Benign recurrent lymphocytic meningitis (Mollaret's meningitis) in Denmark: a nationwide cohort study.

BACKGROUND AND PURPOSE: Data on clinical features and outcomes of benign recurrent lymphocytic meningitis (BRLM) are limited. METHODS: This was a nationwide population-based cohort study of all adults hospitalized for BRLM associated with herpes simplex virus type 2 (HSV-2) at the departments of infectious diseases in Denmark from 2015 to 2020. Patients with single-episode HSV-2 meningitis were included for comparison. RESULTS: Forty-seven patients with BRLM (mean annual incidence 1.2/1,000,000 adults) and 118 with single-episode HSV-2 meningitis were included. The progression risk from HSV-2 meningitis to BRLM was 22% (95% confidence interval [CI] 15%-30%). The proportion of patients with the triad of headache, neck stiffness and photophobia/hyperacusis was similar between BRLM and single-episode HSV-2 meningitis (16/43 [37%] vs. 46/103 [45%]; p = 0.41), whilst the median cerebrospinal fluid leukocyte count was lower in BRLM (221 cells vs. 398 cells; p = 0.02). Unfavourable functional outcomes (Glasgow Outcome Scale score of 1-4) were less frequent in BRLM at all post-discharge follow-up visits. During the study period, 10 (21%) patients with BRLM were hospitalized for an additional recurrence (annual rate 6%, 95% CI 3%-12%). The hazard ratio for an additional recurrence was 3.93 (95% CI 1.02-15.3) for patients with three or more previous episodes of meningitis. CONCLUSIONS: Clinical features of BRLM were similar to those of single-episode HSV-2 meningitis, whilst post-discharge outcomes were more favourable. Patients with three or more previous episodes of meningitis had higher risk of an additional recurrence.

[Genetics and immunology behind herpes simplex encephalitis].

Herpes simplex encephalitis is a devastating neurological disorder with a poor prognosis. For years, it remained elusive why a fraction of otherwise healthy individuals presented with the condition; this lack of insight has hampered understanding of disease pathogenesis and the development of novel effective therapies. However, recent studies have shown that the lack of viral containment can be caused by functionally related monogenic inborn errors of immunity at least in a subset of patients. This knowledge renders prophylactic measures and design of targeted therapies possible, as argued in this review.

[Paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2].

During the COVID-19 pandemic, the emergence of a new condition with hyperinflammatory shock, resembling Kawasaki disease (KD), was reported in children from Western countries strongly affected by SARS-CoV-2. This syndrome was termed paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 infection (PIMS-TS). Despite displaying features similar to KD, studies demonstrated a new and more severe disease entity with multiorgan involvement, in particular gastrointestinal symptoms and heart failure, with blood tests consistent with a postinfectious inflammatory condition as summarised in this review.

Human SNORA31 variations impair cortical neuron-intrinsic immunity to HSV-1 and underlie herpes simplex encephalitis.

Herpes simplex virus-1 (HSV-1) encephalitis (HSE) is typically sporadic. Inborn errors of TLR3- and DBR1-mediated central nervous system cell-intrinsic immunity can account for forebrain and brainstem HSE, respectively. We report five unrelated patients with forebrain HSE, each heterozygous for one of four rare variants of SNORA31, encoding a small nucleolar RNA of the H/ACA class that are predicted to direct the isomerization of uridine residues to pseudouridine in small nuclear RNA and ribosomal RNA. We show that CRISPR/Cas9-introduced bi- and monoallelic SNORA31 deletions render human pluripotent stem cell (hPSC)-derived cortical neurons susceptible to HSV-1. Accordingly, SNORA31-mutated patient hPSC-derived cortical neurons are susceptible to HSV-1, like those from TLR3- or STAT1-deficient patients. Exogenous interferon (IFN)-ß renders SNORA31- and TLR3- but not STAT1-mutated neurons resistant to HSV-1. Finally, transcriptome analysis of SNORA31-mutated neurons revealed normal responses to TLR3 and IFN-α/ß stimulation but abnormal responses to HSV-1. Human SNORA31 thus controls central nervous system neuron-intrinsic immunity to HSV-1 by a distinctive mechanism.

Severe capillary leak syndrome with cardiac arrest triggered by influenza virus infection.

Systemic capillary leak syndrome (SCLS), also known as Clarkson syndrome, is a rare disease with potential fatal outcome. The clinical picture involves leakage of fluid and protein from the bloodstream into peripheral tissues, resulting in hypoalbuminaemia, elevated haematocrit, oedema and hypotension. The spectrum of the symptoms ranges from discrete swelling/oedema of extremities to fulminant cardiogenic shock. We present a case with a 52-year-old man diagnosed with SCLS after being resuscitated from cardiac arrest, which was complicated by compartment syndrome. The severe episode of capillary leak was potentially triggered by influenza virus infection. With the benefit of hindsight, he presented with symptoms of SCLS 2 years prior the major acute episode. Here we describe this case and review some aspects of the literature on SCLS, with particular focus on the pathogenesis, treatment/prophylaxis and long-term physical and psychological complications.

[Herpes simplex encephalitis].

Herpes simplex encephalitis (HSE) is a rare disease, although it is the most common form of sporadic encephalitis worldwide. Recently, studies have provided important new insight into the genetic and immunological basis of HSE. However, even in the presence of antiviral treatment, mortality and morbidity remain relatively high. Therefore, precise and early diagnosis together with basic and clinical studies to gain better insight into the pathogenesis of HSE is a prerequisite for the development of improved prophylaxis and treatment of this severe disease.

Incidence and mortality of herpes simplex encephalitis in Denmark: A nationwide registry-based cohort study.

OBJECTIVES: We aimed to investigate the incidence and mortality of herpes simplex encephalitis (HSE) in a nationwide cohort. METHODS: From the Danish National Patient Registry, we identified all adults hospitalised with a first-time diagnosis of HSE in Denmark during 2004-2014. The HSE diagnoses were verified using medical records and microbiological data. Patients were followed for mortality through the Danish Civil Registry System. We estimated age-standardised incidence rates of HSE and 30-day, 60-day, and 1-year cumulative mortality. Furthermore, we assessed whether calendar year, age, gender, level of comorbidity, virus type, and department type was associated with HSE mortality. RESULTS: We identified a total of 230 cases of HSE. Median age was 60.7 years (interquartile range: 49.3-71.6). The overall incidence rate was 4.64 cases per million population per year (95% confidence interval: 4.06-5.28). The cumulative mortality within 30 days, 60 days, and 1 year of the HSE admission was 8.3%, 11.3%, and 18.6%, respectively. Advanced age and presence of comorbidity were associated with increased 60-day and 1-year mortality. CONCLUSIONS: This nationwide study of verified HSE found a higher incidence than reported in previous nationwide studies. Presence of comorbidity was identified as a novel adverse prognostic factor. Mortality rates following HSE remain high.

XIAP deficiency and MEFV variants resulting in an autoinflammatory lymphoproliferative syndrome.

A 16-year-old boy of Caucasian ethnicity was evaluated for recurrent febrile episodes occurring during most of his life without establishment of any microbial aetiology. During febrile episodes he developed extensive splenomegaly, lymphadenopathy, anaemia, severe abdominal pain and general malaise. Lymph node biopsies demonstrated inflammation and sinus histiocytosis but no malignancy or granuloma. The patient underwent seroconversion for Epstein-Barr virus (EBV) infection during the hospitalisation. Genetic testing identified a hemizygous frameshift mutation in the X linked inhibitor of apoptosis (XIAP)-gene as well as variants in the MEFV gene indicating Familial Mediterranean Fever (FMF). XIAP expression was markedly reduced in the patient, while a functional assay assessing tumour necrosis factor (TNF)α production of monocytes in response to NOD2 stimulation displayed reduced activity. We suggest that the heterozygous MEFV variants and the hemizygous XIAP variant in combination triggered the prolonged and pathological inflammatory response to EBV infection.

Validity of the coding for herpes simplex encephalitis in the Danish National Patient Registry.

BACKGROUND: Large health care databases are a valuable source of infectious disease epidemiology if diagnoses are valid. The aim of this study was to investigate the accuracy of the recorded diagnosis coding of herpes simplex encephalitis (HSE) in the Danish National Patient Registry (DNPR). METHODS: The DNPR was used to identify all hospitalized patients, aged ≥15 years, with a first-time diagnosis of HSE according to the International Classification of Diseases, tenth revision (ICD-10), from 2004 to 2014. To validate the coding of HSE, we collected data from the Danish Microbiology Database, from departments of clinical microbiology, and from patient medical records. Cases were classified as confirmed, probable, or no evidence of HSE. We estimated the positive predictive value (PPV) of the HSE diagnosis coding stratified by diagnosis type, study period, and department type. Furthermore, we estimated the proportion of HSE cases coded with nonspecific ICD-10 codes of viral encephalitis and also the sensitivity of the HSE diagnosis coding. RESULTS: We were able to validate 398 (94.3%) of the 422 HSE diagnoses identified via the DNPR. Hereof, 202 (50.8%) were classified as confirmed cases and 29 (7.3%) as probable cases providing an overall PPV of 58.0% (95% confidence interval [CI]: 53.0-62.9). For "Encephalitis due to herpes simplex virus" (ICD-10 code B00.4), the PPV was 56.6% (95% CI: 51.1-62.0). Similarly, the PPV for "Meningoencephalitis due to herpes simplex virus" (ICD-10 code B00.4A) was 56.8% (95% CI: 39.5-72.9). "Herpes viral encephalitis" (ICD-10 code G05.1E) had a PPV of 75.9% (95% CI: 56.5-89.7), thereby representing the highest PPV. The estimated sensitivity was 95.5%. CONCLUSION: The PPVs of the ICD-10 diagnosis coding for adult HSE in the DNPR were relatively low. Hence, the DNPR should be used with caution when studying patients with encephalitis caused by herpes simplex virus.

A STAT1-gain-of-function mutation causing Th17 deficiency with chronic mucocutaneous candidiasis, psoriasiform hyperkeratosis and dermatophytosis.

During recent years, inborn errors of human IL-17 immunity have been demonstrated to underlie primary immunodeficiencies with chronic mucocutaneous candidiasis (CMC). Various defects in receptors responsible for sensing of Candida albicans or downstream signalling to IL-17 may lead to susceptibility to Candida infection. While CMC is common in patients with profound T cell immunodeficiencies, CMC is also recognised as part of other immunodeficiencies in syndromic CMC, or as relatively isolated CMC disease. We describe a 40-year-old woman with a clinical picture involving cutaneous bacterial abscesses, chronic oral candidiasis and extensive dermatophytic infection of the feet. By whole exome sequencing, we identified a STAT1-gain-of-function mutation. Moreover, the patient's peripheral blood mononuclear cells displayed severely impaired Th17 responses. The patient was treated with antifungals and prophylactic antibiotics, which led to resolution of the infection. We discuss the current knowledge within the field of Th17 deficiency and the pathogenesis and treatment of CMC.