Conditions

Thrombocytopaenia is a condition in which there are too few platelets in the blood.

Platelets are cells which help in clot formation. The normal platelet value ranges between 150,000 to 450,000/microL, and thrombocytopaenia is diagnosed at values below 150,000 platelets/microL.

Causes

Platelet numbers can be decreased by either reduced production in the bone marrow, or increased breakdown of cells. Conditions of decreased production are:

  • systemic infections, viral (rubella, mumps, hepatitis)or bacterial
  • congenital or acquired bone marrow aplasia (non-functioning) such as Fanconi anaeamia, aplastic anaemia, leukaemia
  • after chemotherapy, or irradiation to bone marrow
  • vitamin B12 or folic acid deficiency
  • direct alcohol toxicity
  • HIV infection

Increased destruction is found in:

  • ITP - due to platelet antibodies
  • other immune destruction - for example after transfusion or transplantation
  • thrombotic purpura
  • disseminated intravascular coagulation - widespread clotting literally uses up available platelets
  • hypersplenism - excessive platelet destruction in the spleen
  • post infection - CMV and infectious mononucleosis
  • physical destruction - by heart-lung bypass machines, or giant haemangiomas
  • drug-induced - heparin, quinine and valproic acid are the best known

Symptoms and signs

Many patients have no symptoms and are diagnosed on routine testing for other problems. However, common symptoms are

  • easy bruising or a characteristic rash (small purple spots called petechiae)
  • nosebleeds or bleeding of the gums and inside the mouth
  • menorrhagia - abnormally heavy menstrual bleeding
  • prolonged bleeding after minor trauma such as a small cut
  • severe cases may have frank bleeding into the intestines (vomiting blood or blood in the stool) or the brain (heamorrhagic stroke)

Diagnosis

Diagnosis is by a blood test which shows a low platelet count. Establishing the cause of this may involve tests for antibodies, a clotting profile, and a bone marrow biopsy. A peripheral smear for detecting abnormalities of platelets and all other blood cells is essential.

Treatment

This depends on the cause identified for example

  1. withdrawal of a causative drug
  2. removing the spleen
  3. immune suppression by steroids, chemotherapy or radiotherapy
  4. plasmapheresis to remove antibodies
  5. bone marrow transplant

Transfusion of platelets can be used to stop critical bleeding.

Further publications on the topic