Gingival biopsy in thrombotic thrombocytopenic purpura

Current concepts in the diagnosis and management of thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura is a multisystem disease characterized by thrombocytopenia, hemolytic anemia, renal failure, fever, and neurologic abnormalities. Plasma exchange has revolutionized the outcome of this entity from a once fatal disease to a disease that potentially is cured or has prolonged remission. The understanding of the pathophysiology of TTP continues to evolve. Recently, investigators showed that a deficiency in a specific plasma protease responsible for cleaving vWf plays a crucial role in the familial form of TTP. This explains in part why patients usually respond to plasma exchange therapy. The identification of a mutation in a specific gene that belongs to the metalloproteinase family located at chromosome 9q34 could have important therapeutic implications. TTP can be induced by certain drugs, especially immunosuppressants, in the setting of bone marrow and solid organ transplantation. This disease also has been described in association with HIV, pregnancy, cancer, and chemotherapy. TTP remains an ideal example of how knowledge about the etiology of a disease can improve therapeutic interventions.

Thrombotic thrombocytopenic purpura: the systemic clumping "plague"

In thrombotic thrombocytopenic purpura (TTP), a multimeric form of von Willebrand factor (vWf) that is larger than ordinarily found in the plasma causes systemic platelet aggregation under the high-shear conditions of the microcirculation. A divalent cation-activated, vWf-cleaving metalloprotease that metabolizes large vWf multimers to smaller forms in normal plasma is severely reduced or absent in most patients with TTP. The vWf-cleaving metalloprotease either is not produced or is defective in children with chronic relapsing TTP. When the enzyme is provided by the infusion of normal plasma, these patients remain free of TTP symptoms for about three weeks. An IgG autoantibody to the vWf-cleaving metalloprotease is found transiently in many adult patients with acute idiopathic, recurrent, and ticlopidine/clopidogrel-associated TTP. These patients require plasma exchange, i.e., concurrent replacement of the inhibited vWf-cleaving metalloprotease by plasma infusion and plasmapheresis. The vWf-cleaving metalloprotease is present in fresh-frozen plasma, in cryoprecipitate-depleted plasma (cryosupernatant), and in plasma that has been treated with solvent and detergent. The pathophysiology of platelet aggregation in bone marrow transplantation/chemotherapy-associated thrombotic microangiopathy, and in the hemolytic-uremic syndrome, is not established. In neither condition is there a severe decrease in plasma vWf-cleaving metalloprotease activity.

Thrombotic thrombocytopenic purpura: understanding a disease no longer rare

Serial studies of plasma samples from patients during episodes of thrombotic thrombocytopenic purpura (TTP) have often shown either the presence of unusually large (UL) von Willebrand factor (vWf) multimers or, alternatively, absence of the largest plasma vWf forms. The presence of ULvWf multimers in TTP patient plasma may reflect impaired processing of the ULvWf forms released from endothelial cells. The disappearance of ULvWf and large vWf multimers in some TTP patient plasma samples during acute TTP episodes may be predominantly because these ULvWf forms, along with the largest vWf multimers, bind to platelets and cause aggregation. Serial flow cytometry studies of EDTA-whole blood samples from patients with initial episode, intermittent, and chronic relapsing types of TTP confirm that vWf is the likely aggregating agent, perhaps in association with fluid shear stress. The amount of vWf bound to single platelets has been found to be significantly increased during TTP relapses relative to remission periods in patients with all types of TTP. A substance in normal platelet-poor plasma and the cryoprecipitate-depleted fraction of normal plasma (cryosupernatant) is capable in vitro of reversibly reducing the size of ULvWf multimeric forms released by endothelial cells into the somewhat smaller vWf multimers ordinarily in circulation. This activity has characteristics of a limited disulfide bond reductase. The process of ULvWf breakdown may be made irreversible by the tandem proteolysis, catalyzed by a vWf metalloproteinase, of partially reduced vWf multimers. Several patients with chronic relapsing TTP have decreased or absent plasma vWf metalloproteinase activity, apparently on a congenital basis. Adult initial episode and intermittent TTP patients have been found to have vWf metalloproteinase activity inhibited by an autoantibody during, but not after, TTP epidsodes.

Thrombotic syndromes and autoimmune diseases

Maintenance of blood flow involves the dynamic interactions between the endothelium, circulating cellular components, coagulation factors, and factors involved in fibrinolysis. Autoantibodies, inflammatory cytokines and other undefined triggers in a genetically predisposed person may lead to an imbalance in the equilibrium between the various hemostatic pathways resulting in potentially catastrophic thrombotic events. This article reviews the clinical manifestations and treatment of selected, potentially life-threatening thrombotic syndromes that may occur in association with autoimmune diseases. Special mention is made of thrombotic events associated with Behçet's syndrome.

Southwestern Internal Medicine Conference: Shiga-like toxins in hemolytic-uremic syndrome and thrombotic thrombocytopenic purpura

The majority of cases of hemolytic-uremic syndrome and a smaller proportion of cases of thrombotic thrombocytopenic purpura have recently been shown to result from a toxin produced by enteric bacteria, referred to as verotoxin, or Shiga-like toxin. The predominant toxin-producing bacterial strain in North America is E. coli O157:H7, which causes hemorrhagic colitis in humans after ingestion of contaminated meat. The toxin is believed to gain entry to the circulation from the bowel wall; it then binds to specific glycolipid receptors abundant on renal vascular endothelial cells. The toxin inactivates ribosomes inside the cells, thereby killing them and producing the clinical manifestations of hemolytic-uremic syndrome. Recognition of the etiology of hemolytic-uremic syndrome may lead to better prospects for prevention and treatment.

Thrombotic thrombocytopenic purpura related to ticlopidine

4 patients had typical features of thrombotic thrombocytopenic purpura (TTP) after 3 to 8 weeks of ticlopidine therapy. In 2 ticlopidine was the only medication taken before TTP; in another, rechallenge with drugs other than ticlopidine that the patient had been taking did not produce relapse. In all patients the delay between start of ticlopidine and TTP was in the same range as the latent period before ticlopidine-induced neutropenia. No relapse occurred in the 4 to 43 months of follow-up in the 3 surviving patients.

The gingival biopsy in the diagnosis of thrombotic thrombocytopenic purpura

Gingival biopsy specimens from five patients with a clinical diagnosis of thrombotic thrombocytopenic purpura (TTP) were reviewed. All biopsy specimens demonstrated the characteristic histologic lesion associated with TTP. Review of the literature showed an average diagnostic yield of 37% (30/81) for this procedure. The increase in diagnostic correlation in this study may be explained in part by the marked degree of disease expression in the patients who underwent gingival biopsy. Three of the five patients who underwent gingival biopsies ultimately died of their disease. In addition, a persistent search through multiple serial sections for the characteristic lesion, beyond the usual three levels, was performed. Despite the disparity in diagnostic yield, we consider the gingival biopsy to be a safe diagnostic correlate of TTP because of easy access, rich vascularity, and low surgical morbidity. Furthermore, we recommend biopsy, as Goodman and colleagues have, only in areas of the gingiva that appear clinically normal and free of inflammation in order to reduce misinterpretation as a consequence of false-positive intraluminal fibrin thrombi that may occur with inflammation.

Rocky Mountain spotted fever presenting as thrombotic thrombocytopenic purpura

A patient presented with findings compatible with thrombotic thrombocytopenic purpura. The diagnosis of Rocky Mountain spotted fever was also considered because the patient was a hunter in a tick-infested area. He was treated for both diagnoses. The patient recovered and a diagnosis of Rocky Mountain spotted fever was confirmed by serologic methods. Clinical symptoms and hematologic parameters of severe Rocky Mountain spotted fever may resemble thrombotic thrombocytopenic purpura, implying that there may be similarities in the pathophysiology of both disorders.

Thrombotic thrombocytopenic purpura and systemic lupus erythematosus

We report two patients with systemic lupus erythematosus who subsequently developed thrombotic thrombocytopenic purpura. In each case the coexistence of these two conditions was confirmed by pathological findings. Both patients responded to treatment, but one eventually died. A review of the literature suggests a possible relationship between the two disorders.

Microangiopathic anemia observed after treatment of epidermoid carcinoma with mitomycin C and 5-fluorouracil

Two patients with epidermoid carcinoma treated with mitomycin-C (Mit-C) and 5-fluorouracil (5-FU) developed microangiopathic hemolytic anemia (MAHA), renal failure, and altered mental status. Patient 1 was free of metastatic disease, on maintenance Mit-C and 5-FU when MAHA changes appeared. Patient 2 had recurrent carcinoma in the pelvic area when MAHA changes appeared. In both patients, MAHA changes and neurologic function improved after exchange plasmapheresis. This is the first report of epidermoid carcinoma manifesting MAHA changes after chemotherapy. Speculation as to pathogenesis and appropriate therapy are discussed.