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Hyperviscosity Syndrome in Dogs

High blood viscosity, a thickening of the blood, typically results from markedly high concentration of blood plasma proteins, although it can also result (rarely) from an extremely high red blood cell count. It is most frequently seen as a paraneoplastic syndrome (the consequence of the presence of cancer in the body), and is often associated with multiple myeloma (a cancer of the plasma cell) and other lymphoid tumors or leukemias.

The clinical signs that are associated with hyperviscosity are caused by reduced blood flow through smaller vessels, high plasma volume, and associated coagulopathy (a defect in the body's mechanism for blood clotting). There are no gender or breed predilections, and it is more common in older dogs.

Symptoms and Types

• No consistent signs
• Loss of appetite (anorexia)
• Lethargy
• Depression
• Excessive urination and excessive thirst
• Blindness, unsteadiness
• Bleeding tendencies
• Seizures and disorientation
• Rapid heartbeat and rapid breathing if congestive heart failure present owing to volume overload
• Nosebleed or other bleeding in the mucus membranes
• Visual deficits associated with engorged retinal vessels, retinal hemorrhage or detachment, and optic swelling

Causes

• Multiple myeloma and plasma cell tumors
• Lymphocytic leukemia or lymphoma
• Marked polycythemia (a net increase in the total number of blood cells)
• Chronic atypical inflammation with monoclonal gammopathy (in which an abnormal protein has been detected in the blood [tick fever can cause this in dogs])
• Chronic autoimmune disease (e.g., systemic lupus rheumatoid arthritis)

Diagnosis

Hyperviscosity is a syndrome, not a final diagnosis; however, your veterinarian will want to know what accounts for the symptoms. Your veterinarian will perform a thorough physical exam on your pet, taking into account the background history of symptoms and possible incidents that might have led to this condition. A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, and a urinalysis. Your doctor will be specifically looking at total plasma protein count and evidence of blood disorders. Once a diagnosis has been confirmed, your veterinarian will work out a treatment plan.