The following is a summary of “Herpes Simplex Virus Encephalitis in Patients With Autoimmune Conditions or Exposure to Immunomodulatory Medications,” published in the May 2024 issue of Neurology by Tang et al.
In adults Herpes simplex virus type 1 (HSV-1) is a leading cause of infectious encephalitis, accounting for 15% to 40% of cases.
Researchers conducted a retrospective study investigating how immune system factors, such as autoimmune diseases, medications, and other health conditions, relate to HSV encephalitis (HSVE).
They utilized data from the US Medicaid Analytic eXtract (2007 to 2010) in 29 highly populated American states. Initially, the populace accessed the raw occurrence of HSVE. Following this, adult HSVE cases were matched with a suitable enrollment duration (12 months before HSVE diagnosis) to a larger HSVE-free control group. In a case-control study, the link between HSVE and autoimmune diseases and immunosuppressive/immunomodulatory medications was examined. Analyses were adjusted for sociodemographic factors, the Charlson Comorbidity Index, and non-autoimmune comorbidities.
The results showed that the adult incidence of HSVE has ∼3.01 per 105 person-years. A comparison was made between 951 HSVE cases and 95,100 age and sex-matched controls. The population of HSVE exhibited higher rates of medical comorbidities than the control group. The association between HSVE and autoimmune conditions was robust (aOR 2.6; 95% CI 2.2–3.2). Similarly, the association between HSVE and immunomodulating medications had an OR of 2.2 (CI 1.9–2.6), even after covariate adjustment. Incorporating both exposures in regression models, the associations remained strong, OR 2.3 (CI 1.9–2.7) for autoimmune disease and 2.0 (CI 1.7–2.3) for immunosuppressive and immunomodulatory medications.
Investigators concluded that a large, national population study revealed a strong association between HSVE and pre-existing autoimmune disease alongside prior use of immunosuppressive and immunomodulatory medications.