Follow-up Evaluation of Patients with Hereditary Thrombotic Thrombocytopenic Purpura (hTTP) from the International Hereditary TTP Registry: Incidence of Acute Disease Episodes with or without Regular Prophylactic Plasma Infusions

E. Tarasco^1,2, L. Bütikofer³, G. Sinkovits⁴, Z. Prohászka⁴, A.S. von Krogh⁵, P.N. Knöbl⁶, K.D. Friedman⁷, J.N. George⁸, I. Aebi-Huber^1,2, K.A. Jalowiec¹, Z. Cermakova⁹, M. Górska-Kosicka¹⁰, J. Windyga¹⁰, I. Hrachovinova¹¹, C.R. Largiadèr¹², M. Matsumoto¹³, B. Lämmle^1,14, J.A. Kremer Hovinga^1,2

¹Inselspital, University Hospital of the University of Bern, Department of Hematology and Central Hematology Laboratory, Bern, Switzerland, ²University of Bern, Department for BioMedical Research (DBMR), Bern, Switzerland, ³University of Bern, CTU, Bern, Switzerland, ⁴Research Laboratory, 3rd Department of Internal Medicine and MTA-SE Research Group of Immunology and Hematology, Budapest, Hungary, ⁵St Olavs Hospital Trondheim University Hospital, Department of Hematology, Trondheim, Norway, ⁶University of Vienna, Division of Hematology and Hemostasis, Department of Medicine 1, Vienna, Austria, ⁷Medical College of Wisconsin, Division of Hematology and Oncology, Milwaukee, United States, ⁸University of Oklahoma Health Sciences Center, Department of Biostatistics and Epidemiology, College of Public Health, Oklahoma City, United States, ⁹University Hospital Ostrava, Blood Center, Ostrava, Czech Republic, ¹⁰Institute of Hematology and Transfusion Medicine, Department of Disorders of Hemostasis and Internal Medicine, Warsaw, Poland, ¹¹Institute of Hematology and Blood Transfusion, NRL for Hemostasis, Prague, Czech Republic, ¹²Inselspital, University Hospital of the University of Bern, Bern, Switzerland, ¹³Nara Medical University, Department of Blood Transfusion Medicine, Nara, Japan, ¹⁴University Medical Center Mainz, Center for Thrombosis and Hemostasis, Mainz, Germany

Abstract Number: PB1872

Meeting: ISTH 2020 Congress

Theme: Thrombotic Microangiopathies » ADAMTS13 and TTP

Background: Hereditary Thrombotic Thrombocytopenic Purpura (hTTP) is an ultra-rare autosomal-recessively inherited disorder characterized by recurring acute episodes of thrombotic microangiopathy. Patients have a variable disease course and little is known about the annual rate of acute episodes.

Aims: This study reports the incidence of acute episodes in hTTP patients enrolled in the International Hereditary TTP Registry during follow-up.

Methods: At the end of 2019, we had enrolled 139 confirmed hTTP patients. Prospective follow-up data of 87 hTTP patients from enrollment until 12/2019 were analyzed.

Results: The 87 hTTP patients were followed for 4.2 years (median; range 0-15 years). The median age at overt disease onset and at clinical diagnosis was 4.6 years (range 0-70) and 18 years (range 0-70), respectively.18 female and 25 male patients received regular prophylactic plasma infusions, 11 females and 14 males did not. Prophylaxis was temporarily withheld in 12 females and 6 males (Figure).
109 acute episodes were reported during follow-up in 41/87 patients: 74 in patients with and 35 in patients without prophylaxis. This results in annual episode rates/patient-year of 0.44 (95%CI 0.33-0.58) and 0.16 (95%CI 0.10-0.24) in female and male patients under prophylaxis, respectively; and of 0.38 (95%CI 0.24-0.57) and 0.23 (95%Cl 0.12-0.41) in females and males not under prophylaxis, respectively.
We prospectively followed 13 pregnancies in 5 patients: 6 in 3 women under plasma prophylaxis installed before pregnancy, and 7 in 2 women receiving plasma infusion only during pregnancy. Five acute episodes occurred resulting in one abortion.

Conclusions: Current prophylactic plasma infusions (about 1-3 plasma units every 1-4 weeks) are often insufficient to prevent acute episodes. Patients under prophylaxis have a similar incidence of acute episodes as those not under prophylaxis. Females seem to suffer more frequent acute episodes than males, not attributable to pregnancy alone. Further prospective follow-up will provide robustness of our estimates.

To cite this abstract in AMA style:

Tarasco E, Bütikofer L, Sinkovits G, Prohászka Z, von Krogh AS, Knöbl PN, Friedman KD, George JN, Aebi-Huber I, Jalowiec KA, Cermakova Z, Górska-Kosicka M, Windyga J, Hrachovinova I, Largiadèr CR, Matsumoto M, Lämmle B, Kremer Hovinga JA. Follow-up Evaluation of Patients with Hereditary Thrombotic Thrombocytopenic Purpura (hTTP) from the International Hereditary TTP Registry: Incidence of Acute Disease Episodes with or without Regular Prophylactic Plasma Infusions [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/follow-up-evaluation-of-patients-with-hereditary-thrombotic-thrombocytopenic-purpura-http-from-the-international-hereditary-ttp-registry-incidence-of-acute-disease-episodes-with-or-without-regular/. Accessed January 28, 2022.

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