MASP2 and herpes simplex encephalitis: To date, other genetic etiologies unrelated to type I IFN have also been identified, including the RNA lariat debranching enzyme DBR1 gene in childhood cases, the MASP2 gene reported in adult HSE patients and involved in the innate immune complement system13,14, and the small nucleolar RNA-encoding SNORA31 gene identified in five HSE patients of various ages and involved in the neuronal antiviral response15.