The Thrombocytopenia reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Thrombocytopenia

Thrombocytopenia (or -paenia, or thrombopenia in short) is the presence of relatively few platelets in blood.

Generally speaking a normal platelet count ranges from 150,000 and 450,000 per mm³. These limits, however, are determined by the 2.5th lower and upper percentile, and a deviation does not necessary imply any form of disease.

Table of contents

1 Signs and symptoms 2 Diagnosis 3 Causes 4 Treatment

Signs and symptoms

Often, low platelet levels do not lead to clinical problems; rather, they are picked up on a routine full blood count. Occasionally, there may be bruising, nosebleeds and/or bleeding gums.

It is vital that a full medical history is elicited, to ensure the low platelet count is not due to a secondary process.

Diagnosis

Laboratory tests might include: full blood count, liver enzymes, renal function, vitamin B12 levels, folic acid levels, erythrocyte sedimentation rate.

If the cause for the low platelet count remains unclear, bone marrow biopsy is often undertaken, to differentiate whether the low platelet count is due to decreased production or peripheral destruction.

Causes

Decreased platelet counts can be due to a number of disease processes:

• decreased production
  • vitamin B12 or folic acid deficiency
  • leukemia or myelodysplastic syndrome
• peripheral destruction
  • immune thrombocytopenic purpura (ITP)
  • thrombotic thrombocytopenic purpura (TTP)
  • hemolytic-uremic syndrome (HUS)
  • disseminated intravascular coagulation (DIC)
  • paroxysmal nocturnal hemoglobinuria
  • antiphospholipid syndrome
  • medication-induced (mainly anticoagulants):
    • heparin-induced thrombocytopenia (HIT or white clot syndrome): this is the most common cause of thrombocytopenia in a hospitalized population - it leads to paradoxical thrombosis (HITT, where the last T is for thrombosis)
    • abciximab-induced thrombocytopenia

In some tropical countries, dengue infection is a known rather common cause of thrombocytopenia associated with fever.

Treatment

Low platelet count does generally not warrant treatment, unless there is bleeding or the count is very low. In severe bleeding, platelet transfusion can be necessary.

Bleeding disorders can occasionally be treated by intranasal desmopressin (ddAVP), which increases plasma levels of factor VIII and von Willebrand factor, two coagulation proteins.

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