Multiple myeloma, IgA cryoglobulinemia and serum hyperviscosity in a dog.

Clinical signs of hyperviscosity syndrome in a 6-year-old dog included listlessness, polydipsia, anorexia, vomiting, and recurrent bleeding from the gums. Fundoscopy showed the typical retinal changes associated with this syndrome. A polymeric IgA cryoglobulin characterized in the dog's serum was later isolated and structurally studied. It was found to contain J chain but no secretory component. The heavy and light chains were covalently bound.