People with congenital TTP are born with the condition. It remains with them throughout their life.
There is a mistake in the gene that tells the body how to make the enzyme ADAMST13, therefore, the ADAMST13 is missing.
It affects males and females equally, and the condition is inherited from parents where each parent has half of the nonworking gene. The parents will not have the condition themselves as they only have half nonworking gene.
Here you can see how the inheritance pattern works:
Diagram courtesy of www.newbornscreening.info
Congenital TTP is even more rare than the acquired form. As of 2007 there are approximately 15 cases in the UK.
Symptoms of a patient (baby or small child) with congenital TTP include:
- Jaundice. An exchange transfusion using whole blood may be needed
- Low platelet count
- Tummy upset
- Petechiae or purpura (red pin prick rash)
Children with TTP usually present with symptoms at times of stress. When the body is stressed von Willebrand factor (see What is TTP?) is released into the blood.
Ordinarily if the body has a small amount of ADAMST13 it can cope. If stressed, it is unable to deal with the extra von Willebrand that is produced and cannot break it down.
Following presentation, some children will have TTP all of the time, some will have frequent relapses and some will have infrequent relapses.
Treatment for congenital TTP in children is to use donor fresh frozen plasma (FFP) which contains the missing enzyme (ADAMST13) or a Factor VIII concentrate that is used with Haemophilia patients known as BPL 8Y.