Boxers: Dogs with Serious Heart Conditions

Boxers are prone to a rapidly progressive hereditary heart disease that is often diagnosed too late to be treated effectively. However, the discovery of a physiological biomarker for this condition could revolutionize its management and even lead to its eradication in this dog breed.   Boxers are a breed of dog genetically predisposed to developing a heart condition called arrhythmogenic right ventricular cardiomyopathy. This slowly progressive, degenerative disease of the myocardium causes heart rhythm disorders not only in dogs but also in humans and cats. However, in Boxers, more than 3% of dogs are affected and, furthermore, develop a specific form of the disease that is often asymptomatic. Arrhythmogenic cardiomyopathy has long been classified as a dilated cardiomyopathy; however, in Boxers, the condition exhibits specific characteristics, such as the absence of marked ventricular dilation, the presence of ventricular premature beats, atrial fibrillation (rare), and histological features that have led to its classification as a distinct entity. Unfortunately, it is not uncommon for arrhythmogenic right ventricular cardiomyopathy to go unnoticed until a fatal outcome occurs. The first clinical signs often appear late, leading to cardiac arrhythmias, cardiac hypertrophy, or even sudden and unexpected death. The disease affects the cellular junctions of the heart muscle known as desmosomes. These gradually weaken, causing the heart cells to separate, which in turn leads to the formation of scar tissue. Often, this failure is not detected until the disease is already well advanced… or upon the animal’s death. To have any hope of treating this disease, it is therefore imperative to detect it well in advance. But for now, screening remains very basic (checking for a family history, echocardiogram, data recorded via a portable heart monitor), which means that in most cases, right ventricular arrhythmogenic cardiomyopathy is not detected until the animals are 5 or 6 years old, which is very late. By that age, the dogs have generally already been bred and have passed this condition on to their offspring. Until the genetic cause or a specific marker for the disease is identified, it will be difficult to eliminate this hereditary disease from Boxer bloodlines, and it will continue to be a problem. It was in humans that researchers found answers. In 2018, a Canadian cardiologist specializing in arrhythmogenic right ventricular dysplasia identified an antibody specific to the disease. The anti-DSG2 antibody was detected in nearly all of his patients but was absent in healthy individuals. And this correlation is also found in pedigree Boxer dogs. According to veterinarians, the study conducted on Boxers is still preliminary and too limited to allow for concrete generalizations. However, a clinical trial, funded by the American College of Veterinary Internal Medicine (ACVIM), is currently underway. Its objective is to confirm the role of the anti-DSG2 antibody as a potential biomarker for arrhythmogenic right ventricular cardiomyopathy in Boxers. Earlier screening for the disease could reduce its prevalence in this breed, or even eliminate it entirely, by selecting healthy breeding dogs from a very young age. For affected dogs, this would allow for closer monitoring of clinical signs and earlier, more appropriate treatment. The stakes are therefore high.