Hematology Morphology Forum

Introduction: Thrombotic thrombocytopenic purpura (TTP) is characterized by a reduction in the von Willebrand cleavage protein ADAMTS-13, mainly as a consequence of autoimmunity. Plasma exchange (PEx) is standard, achieving complete remission (CR) in 77–83% of cases, but rates are variable depending on ADAMTS-13 activity and relapse is frequent in patients with <10%. Thus, an effective front-line immunosuppressive treatment is needed.

Materials and methods: We administered PEx daily until CR and rituximab 100 mg/dose/week for 4 consecutive weeks to 10 patients with a first TTP episode and 1 relapsed patient (8 females (72%) and 3 males (28%)). Median age was 34 years (15–46) and laboratory parameters at diagnosis were as follows: platelets 11?×?10⁹/l (range 7–27.4?×?10⁹/l), lactate dehydrogenase 1822?U/l (range 705–8220?U/l, normal 70–180?U/l), and haemoglobin 6?g/dl (range 4.2–11.8?g/dl). ADAMTS-13 activity was determined in eight patients and was <10% in all. ADAMTS-13 autoantibody titre was determined in seven patients and was >15?units/ml in all (ref: negative <12, undetermined 12–15, positive >15?units/ml); Shiga toxin was negative in all patients. The median number of PEx until CR was 7 (range 4–12); prednisone 1?mg/kg was administered to six patients.

Results: The median follow-up was 22 months (range 4–49) and the estimated 2-year relapse-free survival was 89%; one HIV+ patient relapsed at 8 months follow-up. No complications related to PEx or rituximab were reported.

Conclusions: Our study suggests that low-dose rituximab and PEx are effective as front-line treatment for acute TTP; however, a prospective trial is needed to demonstrate whether low-dose rituximab is as effective as the conventional dose.