Hyperviscosity syndrome

Overview

Hyperviscosity syndrome (HVS) is a clinical condition that results from increased blood thickness (viscosity), leading to impaired blood flow and reduced oxygen delivery to tissues. This syndrome is most commonly associated with hematologic disorders such as Waldenström’s macroglobulinemia, multiple myeloma, and polycythemia vera. The increased viscosity can cause a wide range of symptoms, including visual disturbances, neurological deficits, and bleeding. Hyperviscosity syndrome is a medical emergency and requires prompt diagnosis and treatment.

Causes

The underlying cause of HVS is the excessive concentration of blood components, which increases resistance to blood flow. The most common causes include:

• Waldenström’s macroglobulinemia: Overproduction of IgM antibodies increases serum viscosity

• Multiple myeloma: High levels of monoclonal IgA or IgG proteins

• Polycythemia vera: Elevated red blood cell mass increases whole blood viscosity

• Leukemia: High white blood cell counts can lead to sludging and hyperviscosity

• Severe dehydration: Can temporarily increase blood concentration and viscosity

The type of protein or cell causing hyperviscosity varies depending on the underlying disease.

Symptoms

The symptoms of hyperviscosity syndrome typically result from sluggish blood flow and reduced perfusion to vital organs. Common symptoms include:

• Visual disturbances: Blurred vision, double vision, or vision loss

• Neurologic symptoms: Headache, dizziness, vertigo, confusion, or even coma

• Bleeding: Nosebleeds, gum bleeding, easy bruising due to platelet dysfunction

• Fatigue and weakness

• Shortness of breath

• Hearing changes: Tinnitus or hearing loss

Symptoms may appear gradually or develop rapidly depending on the rate and severity of viscosity increase.

Diagnosis

Diagnosis of hyperviscosity syndrome involves both clinical assessment and laboratory testing. Key diagnostic steps include:

• Serum viscosity measurement: Direct testing of plasma viscosity (values >4 centipoise are typically symptomatic)

• Complete blood count (CBC): To assess red and white cell counts and hematocrit

• Serum protein electrophoresis (SPEP): To detect monoclonal proteins

• Immunofixation: To identify specific types of immunoglobulins (IgM, IgA, etc.)

• Fundoscopic exam: May reveal dilated, tortuous retinal veins or retinal hemorrhages

Diagnosis also includes identifying and confirming the underlying hematologic disorder responsible for HVS.

Treatment

Prompt treatment is critical to reduce blood viscosity and prevent complications. Treatment strategies include:

• Plasmapheresis: The primary emergency treatment for removing excess immunoglobulins (especially IgM) from the blood

• Hydration: IV fluids to reduce blood concentration and improve flow

• Cytoreductive therapy: Chemotherapy or other disease-specific treatment to reduce production of abnormal cells or proteins (e.g., rituximab for Waldenström’s)

• Phlebotomy: Used in cases like polycythemia vera to remove excess red blood cells

• Supportive care: Including oxygen therapy and treatment of any bleeding complications

Treatment is tailored based on the underlying condition and the severity of symptoms.

Prognosis

The prognosis of hyperviscosity syndrome depends on the underlying cause, the timeliness of diagnosis, and the effectiveness of treatment. With prompt plasmapheresis and disease-specific management, symptoms often improve rapidly. However, untreated HVS can lead to serious complications, including stroke, organ failure, and death. Long-term prognosis varies depending on the primary hematologic disorder, making ongoing management essential for preventing recurrence.