Excess Plasma Proteins in the Blood (Hyperviscosity) in Cats

By PetMD Editorial on Apr. 11, 2010

Hyperviscosity Syndrome in Cats


Thickening of the blood, medically referred to as hyperviscosity, or high blood viscosity, 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 though it is generally rare in cats, when it does occur, it is more frequently found in older cats.


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




  • 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)
  • Chronic autoimmune disease (e.g., systemic lupus rheumatoid arthritis)



Hyperviscosity is a syndrome, not a final diagnosis; however, your veterinarian will want to know what accounts for the symptoms. veterinarian will perform a thorough physical exam on your cat, 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.  



Generally, cats that present with this disease are treated on an inpatient basis. It will be the underlying disease that will be the focus of the treatment. The total treatment plan will be based upon whether the symptoms are being caused by cancer or by an inflammatory condition.

Living and Management


Even after you take your cat home, your veterinarian will want to monitor your cat's serum or plasma proteins frequently to mark the effectiveness of the treatment. Follow-up blood tests will also be conducted, along with urinalyses from time to time, to determine how well your cat is dealing with the disease.

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