Feline systemic reactive angioendotheliomatosis

A 4-year-old cat presented to the referring veterinarian with lethargy and dyspnoea. Clinical evaluation found there to be pleural and pericardial effusions and a frothy fluid in the airways. The decision to euthanise was taken and samples of heart, lung and liver were submitted for evaluation

Fig 1. Heart; 200x magnification: Myocardial blood vessel (*) exhibiting thrombosis and intravascular endothelial proliferation.

Final Diagnosis

Mild to severe intraluminal endothelial proliferation with partial to complete vascular thrombosis and multifocal myocardial degeneration/necrosis


The changes in the heart are supportive of feline systemic reactive angioendotheliomatosis. This is a rare condition in cats that exhibits similarities to a cutaneous form of disease in people. In people, cases tend to occur in individuals that have immune-mediated conditions (e.g. rheumatoid arthritis) or chronic infections. Extensive work up in feline cases have not observed such a correlation and, at present, this condition remains idiopathic in nature in cats. Despite the systemic nature of the disease in cats, the heart tends to be the organ that is most severely affected. In this case, minor proliferative changes were also observed in scattered portal arterioles in the liver. Ultimately, acute heart failure secondary to large areas of myocardial necrosis is believed to account for the reported clinical findings.