Overview of Acquired Thrombotic Thrombocytopenic Purpura

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EP: 1.Overview of Acquired Thrombotic Thrombocytopenic Purpura

EP: 2.Diagnostic Approach to Acquired TTP

EP: 3.Treatment Options for Acquired TTP

EP: 4.Using Caplacizumab to Treat Acquired TTP

EP: 5.Treatment Considerations for Caplacizumab

EP: 6.The Future of Acquired TTP

X. Long Zheng, MD, PhD: What is acquired TTP? TTP stands for thrombotic thrombocytopenic purpura. Acquired TTP, also known as immune-mediated TTP or ITTP, is a rare but potentially fatal blood disorder resulting from disseminated thrombosis in a small artery and a capillary. Our current understanding of its pathophysiology is as follows: in a healthy individual, blood vessel endothelial cells release the so-called von Willebrand factor, which is a large multimeric protein stored in endothelial cells. There’s an enzyme in plasma that can cleave this ultra-large von Willebrand factor multimer to create a smaller version of it. Then it can stop bleeding when you have a cut, but it doesn’t cause thrombosis, which is a pathological clot. When this enzyme ADAMTS13 is absent—either because you have a mutation in the gene so that the protein cannot be synthesized, or because of autoantibodies that actually targeted this protease and rendered it inactive—these ultra-large von Willebrand factor are left intact in the endothelial cells or in the circulating blood. When that happens, these von Willebrand factor will actually agglutinate the platelets that are flowing by in the blood vessel and capture them, causing aggregates. That causes the microvascular thrombosis. This microvascular thrombosis will lead into the tissue ischemia and also consumptive thrombocytopenia, as well as hemolysis and organ damage. In severe cases, it can cause death.

What are the typical patient characteristics of someone with acquired TTP? TTP can occur in individuals at all ages and with all kinds of racial backgrounds. However, most patients treated in the hospital, we saw, are actually between 30 and 50 years of age, and predominantly African American females. The early recognition of diagnosis of TTP is really the key for reducing mortality. Usually, patients come to the hospital with some nonspecific symptoms including fatigue, headache, fever, pale skin, and a rash on their skin. Some patients may experience abdominal pain, so they come to the emergency department. Some patients may experience weakness, or sometimes they fall on the ground, and they’re found unconscious. These are the common symptoms that are quite nonspecific for TTP.

How prevalent is TTP? TTP is an extremely rare blood disorder. The estimated incidents are about 2 to 6 cases per million per year, so it’s very, very rare.

Transcript edited for clarity.