COVID-19, caused by SARS-CoV-2, frequently manifests as a respiratory disease, including coughing, shortness of breath, fever, and loss of smell. However, additional disease manifestations occur across numerous organ systems, due, at least in part, to venous vasculitis and endotheliitis. COVID-19-associated multisystem inflammatory syndrome in children (MIS-C) was recently identified as a component of SARS-CoV-2 infection. In feline medicine, feline coronavirus is a common pathogen of cats that can lead to a fatal disease called feline infectious peritonitis (FIP). Like COVID-19 in humans, the clinical manifestations of FIP are due to coronavirus-induced venous vasculitis that can also result in a fatal multisystem inflammatory syndrome in cats. As such, studies investigating how feline coronavirus infection can cause disseminated vasculitis in FIP cats will provide new information that can translate to understanding COVID-19 in humans. We argue for a comparative medicine approach for tackling coronavirus diseases.