Intravenous prostacyclin in thrombotic thrombocytopenic purpura: case report and review of the literature

Porcine hematopoietic cell xenotransplantation in nonhuman primates is complicated by thrombotic microangiopathy

Thrombotic microangiopathy (TM) is a serious complication of bone marrow transplantation (BMT) that resembles thrombotic thrombocytopenic purpura (TTP). In attempting to achieve hematopoietic cell chimerism in the pig-to-baboon model, we have observed TM following infusion of high doses (>10(10) cells/kg) of porcine peripheral blood mobilized progenitor cells (PBPC) into baboons. We performed investigations to analyze the pathobiology of this TM and to test therapeutic interventions to ameliorate it. PBPC were obtained by leukapheresis of cytokine-stimulated swine. The initial observations were made in two baboons that underwent a non-myeloablative regimen (NMR) prior to PBPC transplantation (TX) (group 1). We then studied three experimental groups. Group 2 (n = 2) received NMR without PBPC TX. Group 3 (n = 2) received PBPC TX alone. Group 4 (n = 6) received NMR + PBPC TX combined with prostacyclin, low-dose heparin, methylprednisolone, and cyclosporine was replaced by anti-CD40L mAb in five cases. Baboons in groups 1 and 3 developed severe thrombocytopenia (<10,000/mm3), intravascular hemolysis with schistocytosis (>10/high powered field (hpf)), increase in plasma lactate dehydrogenase (LDH) (2500-9000 U/l), transient neurologic changes, renal insufficiency, and purpura. Autopsy on two baboons confirmed extensive platelet thrombi in the microcirculation, and, similar to clinical BMT-associated TM/TTP, no unusually large vWF multimers or changes in vWF protease activity were observed in the plasma of baboons with TM. In group 2, self-limited thrombocytopenia occurred for 10-15 days following NMR. Group 4 baboons developed thrombocytopenia (<20,000/mm3) rarely requiring platelet transfusion, minimal schistocytosis (<3/hpf), minor increase in LDH (<1000 U/l), with no clinical sequelae. We conclude that high-dose porcine PBPC infusion into baboons induces a microangiopathic state with vWF biochemical parameters resembling clinical BMT-associated TM/TTP and that administration of antithrombotic and anti-inflammatory agents can ameliorate this complication.

Thrombotic thrombocytopenic purpura: diagnosis, pathogenesis and modern therapy

Thrombotic thrombocytopenic purpura (TTP) is an uncommon multisystem disorder, sometimes associated with predisposing conditions such as pregnancy, cancer, exposure to certain drugs, bone marrow transplantation and HIV-1 infection. An abnormal interaction between the vascular endothelium and platelets which occurs in certain organs leads to thrombosis, endothelial proliferation, minimal inflammation and micro-angiopathic haemolysis. Recent studies suggest that endothelial cell perturbation and apoptosis caused by an as yet unknown plasma factor(s) may lead to the release of abnormal von Willebrand factor which facilitates the deposition of platelet microthrombi. Exchange transfusions of plasma or plasma-cryosupernatant remain the cornerstone of the treatment of TTP along with corticosteroids, platelet inhibitor drugs, vincristine and splenectomy. In most cases remissions can be attained, and cures are now common-although approximately one-half of the patients will relapse. While relapses are usually milder, they still carry a significant mortality and preventive therapies are not always effective.

[Prostacyclin in the treatment of hemolytic-uremic syndrome: apropos of a case]

A 52 year-old man was hospitalised for acute renal failure with thrombocytopenia and hemolytic anemia without oliguria. A haemolytic-uremic syndrome was diagnosed and prostacyclin infusion was started. Twenty-four hours later, the renal function improved as well as thrombocytopenia and anemia. Recovery occurred after 11 days of treatment. Haemolytic-uremic syndrome treatment is not well codified: plasmaphoresis, fresh frozen plasma, transfusions showed inconstant efficiency and data about prostacycline treatment are rare and often contradictory. Multicentric studies must be started in order to determine the precise benefit of this treatment.

The changing course of thrombotic thrombocytopenic purpura and modern therapy

Thrombotic thrombocytopenic purpura (TTP) is a multisystem disorder of unknown etiology. Pathologically, there appears to be an abnormal interaction between the vascular endothelium and platelets, but the primary event remains uncertain. While historically, TTP was a fatal disease, dramatic improvement in its outcome has occurred over the past two decades with the development of effective therapy. Plasma infusion or exchange remains the cornerstone of the treatment of TTP, along with corticosteroids, platelet inhibitor drugs, vincristine and splenectomy. This review summarizes the clinical findings, what is known of the pathogenesis and the available therapeutic modalities for TTP. In most cases, remissions can be attained and cures are now common. However, approximately half the patients will relapse. The clinical course at relapse is usually milder than the disease at presentation and less aggressive therapy may be needed. However, relapsing TTP still carries a significant mortality and preventive therapies are not always effective. Further progress may have to await an understanding of the fundamental etiology of this disease.