altered situation in study population; not enough patients meeting enrollment criteria

Congenital thrombotic thrombocytopenic purpura (TTP), also called Upshaw-Schulman Syndrome or hereditary or familial TTP is a rare, but severe disease. The purpose of this study is to determine how infusions of plasma to patients with congenital TTP correlate with symptoms and signs of activity of the disease, and to determine why some patients need more frequent infusions of plasma than others to prevent acute attacks of the disease.

Patients with congenital TTP have an inherited lack of function or amount of a protein in plasma called ADAMTS13, that otherwise is responsible for cleaving large von Willebrand-molecules into smaller parts. The patients suffer recurrent attacks of clotting of small blood vessels, that can cause damage to major organs, including the central nervous system. Acute attacks can be treated successfully with infusions of human plasma, and some patients also receive regular plasma therapy for prevention of acute attacks. A small group of patients receive preventive plasma infusions twice or more weekly, indicating a much higher need for plasma than what is otherwise recommended for preventive therapy. Do these patients have an ongoing activity of their disease despite a stimulus? Or a higher turn-over of transfused ADAMTS13? Have these patients developed antibodies against transfused ADAMTS13? Are any symptoms correlated with signs of disease activity?

Inclusion Criteria:

• Confirmed diagnosis of congenital TTP
• On regular prophylactic plasma treatment: > Once weekly (group 1) or >1 <3 times monthly (group 2)
• Between 18 and 65 years
• Capable of understanding and complying with the protocol

Exclusion Criteria:

• Pregnancy
• Acute bout of TTP requiring daily plasma infusions or -exchange for more than 3 days, within the last 2 weeks before intervention period