Hyperviscosity Syndrome

Hyperviscosity refers to any state in which there is increased viscosity of the blood. It may be classified into pleiocytosic, sclerotic and sieric syndromes, according to the blood components involved.

The precise incidence of hyperviscosity syndrome is not known as it may occur in a large number of conditions. Hyperviscosity may occur at any age, but the aetiology of that seen in infants is different from that seen in adults.

Associated Diseases

In adults this is most commonly seen in association with:

• Plasma cell neoplasia
• Myeloma
• Connective tissue diseases
• Chronic hypoxia
• Paraneoplastic syndromes; when it results from the large amounts of circulating immunoglobulins, cryoglobulins, paraproteins or antibodies, or due to an excessive increase in blood cells.

In infants hyperviscosity may occur as a result of the polycythaemia, which develops in response to intrauterine hypoxia, or hypoxia during delivery.¹

Hyperviscosity occurs as a result of a raised haematocrit, or due to increased levels of circulating plasma components.
Many conditions may produce this state including²:

• Waldenströms macroglobulinaemia (most common cause)
• Multiple myeloma
• Polycythaemia rubra vera
• Leukaemia
• Connective tissue disorders e.g.rheumatoid arthritis
• Hyperleukocytosis
• Retinoic acid therapy

Increased viscosity and reduced blood flow may result in a variety of clinical manifestations including:

• CNS:
  • Lethargy
  • Headache
  • Nystagmus
  • Deafness
  • Convulsions
  • Visual
  • Papilloedema
  • Fundal haemorrhages
  • Dilation of the retinal vessels
  • Loss of vision
• CVS:
  • Hypertension
  • Heart failure
• Haematological:
  • Dilutional anaemia
  • Platelet dysfunction ( especially IgA myeloma)
  • Bleeding,
  • Bruising
  • Nose bleeds
  • Bruising
  • Menorrhagia
  • Rectal bleeding
  • Thrombosis
  • Leukocyte dysfunction-sepsis
  • Crossmatch difficulties
• Renal:
  • Renal failure

• Plasma viscosity - increase seen
• FBC and differential cell count
• Blood film may show rouleaux formation
• Platelet count
• Clotting screen

Other investigations to determine the underlying cause e.g. bone marrow aspiration, urine electrophoresis, auto-antibody levels.

Non-Drug

• Patients with a hyperviscosity syndrome should be advised that this may reoccur, and advised to look for signs of bleeding or infection.
• Some conditions producing hyperviscosity may be helped by regular venesection e.g. polycythaemia rubra vera.
• Unfortunately, repeated procedures may lead to iron deficiency. This results in microcytic erythrocytes, that induce higher viscosity than normocytic erythrocytes. This may increase the risk for venoocclusive events.³
• Infants may be treated using partial exchange transfusion.
• In adult patients, plasmapharesis to remove excess numbers of cells, or circulating complexes remains the treatment of choice.⁴1-2 procedures, is advised for the treatment of hyperviscosity syndrome in Waldenström's macroglobulinaemia. In patients who are drug resistant this may be indicated as long term management.⁵

Drugs

The underlying cause of the hyperviscosity syndrome may be treated with chemotherapy where appropriate.

Complications may occur as a result of bleeding, thrombosis or sepsis and may result in neurological deficit, heart failure, renal failure.
Rarely they may prove fatal.

The overall prognosis for any patient will depend on the underlying condition.