Frequently Asked Questions

Q1. My family member was diagnosed with TTP. Do I need to be tested?

Thrombotic thrombocytopenic purpura (TTP) is a rare disorder, and may be acquired (immune-mediated TTP) or the congenital form (hereditary TTP).  iTTP occurs as a result of the patient developing an antibody against the ADAMTS13 protease, resulting in severely deficient ADAMTS13 activity (<10%) that confirms the diagnosis of TTP.  Laboratory testing can be performed to evaluate for the presence of an antibody inhibitor of the ADAMTS13 protease which would confirm the diagnosis of iTTP.  If an antibody cannot be found to explain the severely deficient ADAMTS13 activity, then suspicion would be raised for the diagnosis of hTTP.  The diagnosis of hTTP would then typically be confirmed with genetic testing to document the presence of an ADAMTS13 mutation.  hTTP is much less common (<1 per million of the population) than iTTP (approximately 6/million of the population), with an inheritance pattern that is autosomal recessive, meaning you typically need mutations to be present in both genes in order to develop hTTP.  ADAMTS13 testing could be considered in family members of patients diagnosed with hTTP after consultation with a physician with experience in the diagnosis of TTP.  Family members of patients with the immune-mediated (acquired) form of TTP do not need ADAMTS13 activity testing performed.