ADAMTS-13 levels in patients with a history of thrombotic thrombocytopenic purpura

ADAMTS-13 is involved in the life treatening disease TTP. The protein ADAMTS-13
facilitates the break down of von Willebrand Factor. When the protein is
prefented by antibodies to break down, the vWF thrombosis can occur. TTP is
treated with plasmachange. If TTP is discovered in time, it can be treated
well. Recently it was discovered that patiens with a history of TTP that have
no ADAMTS-13 activity, also have less ADAMTS-13 activity on the lon term.
Possibly a small amount of ADAMTS-13 activity is enough to prevent a TTP
episode, though low amounts of ADAMTTS-13 can cause complaints. Moreover, low
amounts of ADAMTS-13 activity is a possible risk factor for new relapses of
TTP.

Determine the ADAMTS-13 activity in patients with a history of TTP.

50 TTP patients (m/f) with a history of TTP are approached by the TTP patient
association to visit the annual patient day. The patients are asked to fill in
a questionnaire and give permission to donate blood for scientific research.
(cross-section). Blood will be drawn during this day at the UMC Utrecht. The
patient day will be held annually, and every time permission will be asked for
blood withdrawl and filling in the questionnaire (prospective part). In the
future we would like to investigate the relation between TTP and the presence
or absence of ADAMTS-13 with this study design.

Participation is of harly any burden. Patients are asked to fill in a
questionnaire on the history and course of their disease and after consent 10
ml blood is withdrawn by qualified personnel for scientific research. Risk:
hematoma after venpunction.