HSV-1 and HHV-6 Meningoencephalitis in a Child with STAT1 Mutation

Abstract

Introduction: STAT1 is a critical signal transducer for both the interferon gamma receptor and IFN-alpha/beta receptors and is required for responses to herpesviruses. STAT1 defects vary in severity and clinical presentation. STAT1 loss of function (LOF) mutations with Mendelian Susceptibility to Mycobacterial Disease (MSMD) and STAT1 gain of function (GOF) mutations have been described with a wide clinical spectrum, including nontuberculous mycobacteria, disseminated fungal, bacterial, and viral infections in addition to immune dysregulation. We present a 10-year-old female with HSV-1 and HHV-6 meningoencephalitis that was found to have a variant in STAT1. MethodsRetrospective chart review was conducted. Laboratory investigations included lymphocyte immunophenotyping by flow cytometry, lymphocyte proliferation to mitogens and antigens, NK cell functional assays, quantitative immunoglobulins, toll like receptor function defects, genetic evaluation by next generation sequencing, and assays for further evaluation for MSMD, T helper IL17, STAT GOF. ResultsA previously healthy 10-year-old Caucasian female presented with fever, headache, and new-onset seizure with status epilepticus. She was diagnosed with HSV-1 and HHV-6 meningoencephalitis, as CSF PCR panel was positive for HSV-1 and HHV-6. Brain MRI showed findings compatible with HSV-1 encephalitis. She was treated with a 14-day course of acyclovir with no noted neurological sequelae. Infection history was unremarkable except for one episode of otitis media as a child and a couple upper respiratory viral illnesses. Denied prior history of HSV infection. No family history of immunodeficiency disorders. Both parents reported remote history of herpetic gingivostomatitis. Laboratory immune evaluation was remarkable for decreased lymphocyte proliferative response to Candida antigen. Next generation sequencing revealed a variant of uncertain significance in STAT1 (c.295A>G; p.Ile99Val) and did not detect TLR3 or UNC93B1 mutations. ConclusionThe clinical phenotype caused by STAT1 mutations is highly diverse, and there is overlap between GOF and LOF phenotypes, making it difficult to clinically diagnose. Although HSV gingivostomatitis has been reported in a patient with STAT1 GOF, invasive disease, such as meningoencephalitis, has not been reported in those with variants in STAT1.