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What is a blood platelet?

By Dr Mike Bamford
Consultant Paediatrician
and Medical Advisor to the
TAR Syndrome Support Group

TAR syndrome is characterised by low blood platelets (thrombocytopenia) and skeletal defects. The thrombocytopenia improves with time but it can require management in the very early years.

What is thrombocytopenia?

Thrombocytopenia is the medical term for low blood platelets. The platelets (thrombocytes) are elements of the blood that are very important for normal blood clotting. They are very small. They are not cells in themselves but are derived from cells in the bone marrow (called megakaryocytes). In TAR syndrome the megakaryocytes are reduced in number or even absent in the early years. This makes the platelet count low. This leads to a possible tendency for easy bruising or bleeding.

Medical management of thrombocytopenia

Children and adults can function quite well with a reduced count down to about 30,000. Between 30,000 and 100,000 the risk of bleeding is only in extreme circumstances such as severe injury or surgical operation. Below 30,000 a tendency to easy bruising will become more evident and minor injuries may bleed freely e.g. cuts, nosebleeds or bleeding gums.Below around a count of 10,000 there is a risk of affected patients having spontaneous bleeds e.g. in the gut or more serious bleeds with minor injuries.The most worrying type of bleeding would be inside the brain – but fortunately the risk is very small. In TAR syndrome in the first year or so of life the count tends to be between 15,000 and 30,000 although occasionally children have nearly normal counts. The count tends to fall when children have infections and therefore the child may be more prone to bleeding in those circumstances.

If a proven bleed occurs or if there is a severe risk of bleeding a platelet transfusion can be given. This would normally take place in three circumstances:

  1. significant injury
  2. surgery
  3. spontaneous bleed

It is not common medical practice to give a transfusion in circumstances other than these because of the small risk of transfusing blood products.

If a child is likely to require medical transfusions a single donor should be identified to prevent the patient from developing a rejection of donor platelets. It is not usual to give platelet transfusions on the basis of the platelet count alone. In the second and third years of life the platelet count tends to increase towards the norm and the risk of bleeding decreases.

Delivery of a baby with TAR

Because of the risk of bleeding during the birth process the possibility of delivery by caesarian section may be discussed with the obstetrician where the unborn child is known to have the condition.

Prognosis for children with TAR

In the past thrombocytopenia could be very dangerous for children with TAR but with medical advances in blood transfusion it is now extremely rare for children to die as a result of this syndrome.

Possible signs of an internal bleed

Consult your doctor if:
1. your child develops a rash of red pin prick spots (petechiae spots)
2. you notice your child is bruising much more than usual
3. your child develops any unexpected and prolonged bleeding
4. your child is drowsy and unresponsive or seems to be in a lot of pain.


© 1998 Mike Bamford and TAR Syndrome Support Group

[Last modified: 9 September 2001]