Lymphocytosis: A New Genetically Based Syndrome Characterized in the English Bulldog

According to a U.S. retrospective study, some English bulldogs may have been misdiagnosed with cancer. Thus, pedigree dogs presenting with B-cell chronic lymphocytic leukemia may in fact be suffering from a recently described non-cancerous syndrome: B-cell polyclonal lymphocytosis. This discovery provides a better understanding of and allows for more effective management of these two conditions in dogs.   Certain dog breeds are at higher risk of developing a type of cancer called B-cell chronic lymphocytic leukemia. Among them, the English bulldog appears to be genetically predisposed and may have a specific form of this cancer. Clinical signs appear at a significantly younger age, and marked differences are observed on the surface of their B lymphocytes—the immune cells that produce antibodies. These characteristics caught the attention of researchers at the University of Colorado, who wondered whether the dogs actually had B-cell chronic lymphocytic leukemia or whether it was instead another, unknown, and completely different disease with a similar pathophysiology. After selecting 84 bulldogs with high levels of circulating B lymphocytes, the research team analyzed their serum to determine the types of antibodies being produced. Many dogs also had an enlarged spleen, which prompted the researchers to take a closer look at the types of cells developing there. If the results had revealed identical B cells, this would have suggested that they originated from a single cell, pointing to uncontrolled cell proliferation—and thus a likely cancerous origin. But to their surprise, the researchers found that 70% of the bulldogs that had developed clinical signs of B-cell chronic lymphocytic leukemia did not have cancer. This was particularly true of young dogs, some of whom were one or two years old when the first signs of the disease appeared. Three-quarters were males, and half of them also had an enlarged spleen. Most cases also presented with hyperglobulinemia. Rather than being at high risk of developing B-cell chronic lymphocytic leukemia, as was originally thought, English Bulldogs therefore most often develop a benign syndrome that shares many similarities with this neoplasm. The team is seeking to characterize this syndrome in other breeds, although it likely affects English Bulldogs preferentially. An underlying genetic cause is indeed being considered, although this remains to be confirmed and the genetic mutation has yet to be identified. For now, veterinarians know very little about the condition, which does not appear, at this stage, to follow a malignant clinical course. However, the health implications of a consistently elevated B-cell count have not yet been determined. This is an important finding for the care of dogs, particularly English Bulldogs. Thus, a high B-cell count does not necessarily indicate a neoplasm in this breed. A better understanding of this syndrome would help prevent misdiagnosis in certain cases and avoid treating these dogs unnecessarily for a cancer that is not actually present.