BackgroundPlatelet activation has been implicated in the pathogenesis of sickle cell disease (SCD) suggesting antiplatelet agents may be therapeutic. To evaluate the safety of prasugrel, a thienopyridine antiplatelet agent, in adult patients with SCD, we conducted a double-blind, randomized, placebo-controlled study.MethodsThe primary endpoint, safety, was measured by hemorrhagic events requiring medical intervention. Patients were randomized to prasugrel 5 mg daily (n = 41) or placebo (n = 21) for 30 days. Platelet function by VerifyNow® P2Y12 and vasodilator-stimulated phosphoprotein assays at days 10 and 30 were significantly inhibited in prasugrel- compared with placebo-treated SCD patients.ResultsThere were no hemorrhagic events requiring medical intervention in either study arm. Mean pain rate (percentage of days with pain) and intensity in the prasugrel arm were decreased compared with placebo. However, these decreases did not reach statistical significance. Platelet surface P-selectin and plasma soluble P-selectin, biomarkers of in vivo platelet activation, were significantly reduced in SCD patients receiving prasugrel compared with placebo. In sum, prasugrel was well tolerated and not associated with serious hemorrhagic events.ConclusionsDespite the small size and short duration of this study, there was a decrease in platelet activation biomarkers and a trend toward decreased pain.

A high burden of sleep disordered breathing and other sleep-related complaints were identified in the adult sickle cell population. Our results provide important information on this unique population.

Storage of platelets at 4 degrees C causes increased membrane vesiculation and accelerated loss of GPIb. The magnitude of these differences was small, but it may contribute to marked reductions in platelet survival in circulation.

Tumor necrosis factor (TNF), a macrophage secretory protein produced by peripheral blood monocytes from patients with cancer, has been shown to possess cytotoxicity toward tumor cells in vitro. TNF in the blood of individuals with cancer is usually not detectable except with extremely sensitive radioimmunoassay or enzyme-linked immunosorbent assay (ELISA) methods. We have encountered two patients with the rare syndrome of extensive bone marrow necrosis in association with cancer. The first patient presented with marrow failure secondary to necrosis and was found to have adenocarcinoma in thoracic lymph nodes, lung, and marrow lymphatics at autopsy. Plasma tested at two dilutions (1:200 and 1:2,000) contained TNF at a concentration of 8.3 ng/ml, or 80 U/ml by a cytotoxicity assay using LM cells. The presence of TNF was confirmed with immunoblotting. The second patient had a poorly differentiated lymphoid tumor involving bone marrow, pancytopenia, and marrow necrosis. The plasma cytotoxicity assay indicated the presence of 0.7 ng/ml or 7 U/ml TNF. TNF was not detectable in plasma from six other patients with untreated cancer involving bone or bone marrow using either of our methods. The levels of TNF in the two patients with marrow necrosis were greater than those previously measured by others in patients with cancer but were comparable to those noted in patients with lethal sepsis. Since large doses of TNF have been shown to cause organ necrosis in animals, the data presented here are consistent with TNF involvement in mediating the observed marrow necrosis in our patients.

A 64-year-old white male was referred for evaluation of prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT) obtained before elective surgery with initial PT and PTT results of 14.9 and 38.4 seconds, respectively, which corrected to normal in 1:1 mixes with normal plasma. Functional prothrombin assay indicated a level of 51% with thromboplastin as an activator. The prothrombin antigen was 102%. This discordance in the functional and immunologic prothrombin levels was evidence for dysprothrombinemia. Western blotting showed that thrombin was formed at a normal rate in diluted plasma consistent with a mutation within the thrombin portion of prothrombin. DNA was isolated from leukocytes and the thrombin exons were amplified by polymerase chain reaction, cloned, and sequenced. For exon 13, eight clones were sequenced with four clones showing a point mutation in the codon for Arg517, which would result in substitution by Gln. Arg517 is part of the Arg-Gly-Asp(RGD) sequence in thrombin and contributes to an ion cluster with aspartic acid residues 552 and 554. Mutation at this residue most probably distorts the structure of the Na+ binding site in thrombin. This is the first report indicating the critical role of Arg517 in the normal physiological interaction of thrombin with fibrinogen. This dysprothrombin is designated Prothrombin Greenville.