Serum hyperviscosity syndrome associated with IgA multiple myeloma in two dogs

IgA multiple myeloma associated with the hyperviscosity syndrome was diagnosed in two Airedale terriers. Hemorrhagic diathesis was observed in one dog. Treatment with antibiotics, melphalan, and prednisolone resulted in temporary remission in one patient and prolonged remission in the other. The serum hyperviscosity syndrome is not always associated with multiple myeloma because serum viscosity is dependent on chemicophysical properties of serum proteins as well as their concentrations. In dogs, it has been observed in association with IgM and polymerized IgA myeloma proteinemia. Clinical signs which may be associated with the serum hyperviscosity syndrome include cardiac and renal dysfunction, hemorrhagic diathesis, and neurological disturbances. The pathophysiology of the serum hyperviscosity syndrome and hemorrhagic diathesis associated with multiple myeloma in dogs and man is reviewed.