The subserosal and mesenteric lymph vessels are dilated and the mucosa is usually thickened and velvety. On histopathology, there is edema in the submucosa and lamina propria. The lymph vessels are distended with cystic, dilated and frequently ruptured lacteals. There is a build-up of mononuclear cells in the lamina propria, usually plasmacytes and lymphocytes, in the jejunum and also the stomach. The stomach frequently exhibits chronic atrophic gastritis, which in some individuals have been known to progress to gastric carcinoma.
Intestinal villi are abnormal, usually short, blunted and anastomosed.
In one dog, lymphocytic plaques were found throughout the surface of the lungs and intestines. In another dog, the lymph node cytology suggested lymphoma. This disease is appearing to be a whole complex of manifestations, of which the more they look, the more they find. At this point, the cause is totally unknown. Certainly there is a genetic predisposition to the disease, and then something sets it off.