From a genetic viewpoint, several single studies have investigated the association of different single nucleotide polymorphisms (SNPs) of ACE1 (e.g., rs1799752), ACE2 (e.g., rs2285666), or TMPRSS2 (e.g., rs12329760) genes with the severity of COVID-19 [4,5,6]. The gene discussed is TMPRSS2; the disease is COVID-19.