This case series describes rare putative X-chromosomal loss-of-function variants associated with impaired peripheral mononuclear blood cell interferon signaling in 4 young male patients hospitalized with severe coronavirus disease 2019 (COVID-19) in the Netherlands.
Question Are genetic variants associated with severe coronavirus disease 2019 (COVID-19) in young male patients? Findings In a case series that included 4 young male patients with severe COVID-19 from 2 families, rare loss-of-function variants of the X-chromosomal TLR7 were identified, with immunological defects in type I and II interferon production. Meaning These findings provide insights into the pathogenesis of COVID-19.
Importance Severe coronavirus disease 2019 (COVID-19) can occur in younger, predominantly male, patients without preexisting medical conditions. Some individuals may have primary immunodeficiencies that predispose to severe infections caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Objective To explore the presence of genetic variants associated with primary immunodeficiencies among young patients with COVID-19. Design, Setting, and Participants Case series of pairs of brothers without medical history meeting the selection criteria of young (age T; p.[Val795Phe]). In primary peripheral blood mononuclear cells from the patients, downstream type I interferon (IFN) signaling was transcriptionally downregulated, as measured by significantly decreased mRNA expression of IRF7, IFNB1, and ISG15 on stimulation with the TLR7 agonist imiquimod as compared with family members and controls. The production of IFN-gamma, a type II IFN, was decreased in patients in response to stimulation with imiquimod. Conclusions and Relevance In this case series of 4 young male patients with severe COVID-19, rare putative loss-of-function variants of X-chromosomal TLR7 were identified that were associated with impaired type I and II IFN responses. These preliminary findings provide insights into the pathogenesis of COVID-19.