Thrombocytopenia is a common condition in distressed newborns, but little is known about thrombocytopenia in an unselected cohort of neonates. In an attempt to address this issue, a multicenter prospective study was conducted in three obstetrical wards of AP-HP in Paris. We found the frequency of neonatal thrombocytopenia (<150 × 109/L) to approximate 0.9% (48 of 5,632 appropriate samples). An immune mechanism was likely to be the cause of thrombocytopenia in 10 of the 33 cases studied, implying an incidence of 0.3% of immune neonatal thrombocytopenia in the general population. The frequency of alloimmune thrombocytopenia was 1.5/1,000 liveborn neonates, and 1/1,000 when considering anti–HPA-1a allo-immunization. Because thrombocytopenia, whatever its cause, was often silent and delayed, it appears that the only way to detect neonatal thrombocytopenia in time to prevent its potential disastrous complications would be to perform a systematic neonatal blood sampling for platelet count. All cases of ascertained thrombocytopenia should then be screened for an immune mechanism to enable early detection of autoimmune diseases in mothers and careful monitoring of subsequent pregnancies and deliveries, leading to appropriate prevention of potential severe deleterious effects in the offspring.

To cite this article: Gerotziafas GT, Petropoulou AD, Verdy E, Samama MM, Elalamy I. Effect of the anti-factor Xa and anti-factor IIa activities of low-molecular-weight heparins upon the phases of thrombin generation. J Thromb Haemost 2007; 5: 955-62.Summary. Background: Low-molecular-weight heparins (LMWHs), derived from unfractionated heparin (UFH) by different depolymerization procedures, vary in both their relative abilities to enhance the inhibition of FXa (anti-FXa) and thrombin (anti-FIIa), and in their physicochemical properties. Objective: We aimed to profile the inhibition of thrombin generation induced by bemiparin, enoxaparin, nadroparin, dalteparin and tinzaparin in platelet-rich plasma (PRP), and to compare them with UFH and fondaparinux (a synthetic pentasaccharide that specifically enhances FXa inhibition). Methods: Different LMWHs, UFH or fondaparinux were added to normal PRP. Thereafter, tissue factor-triggered thrombin generation was assessed using the ThrombogramThrombinoscope Ò assay. Results: At equivalent anti-FIIa activity concentrations, LMWHs and UFH exhibited similar inhibitory effects upon thrombin generation. However, when used at equivalent anti-FXa activity concentrations, tinzaparin was significantly more active than the other LMWHs at inhibiting thrombin generation, and had similar activity to that of UFH. Enoxaparin, nadroparin and dalteparin all showed similar inhibitory activities. In these experiments, bemiparin exhibited the lowest inhibitory effect on thrombin generation of all the LMWHs. At 0.1 lg mL -1 (0.093 anti-FXa IU mL -1 ), fondaparinux inhibited the rate of thrombin generation by 50%. A 7-fold higher concentration of fondaparinux was required to inhibit the endogenous thrombin potential by 50%. Conclusions: LMWHs have a variable inhibitory effect on thrombin generation in vitro when compared by anti-FXa activity, but are similar when compared by their anti-FIIa activities. The rate of thrombin generation during the propagation phase, rather than the endogenous thrombin potential, is more sensitive to the anticoagulant activity of fondaparinux and the polysaccharide chains of LMWHs possessing only anti-FXa activity.

We conducted a study to assess the incidence and outcome of hemophagocytic histiocytosis (HH) in thrombocytopenic patients with sepsis syndrome or septic shock and to define the possible associations between HH, disseminated intravascular coagulation (DIC), and platelet-associated IgG (PAIgG) in promoting thrombocytopenia. Twenty immunocompetent thrombocytopenic patients were included. Bone marrow aspirates were obtained from each patient to identify hemophagocytic histiocytes. Coagulation parameters, PAIgG levels, and bacterial and viral infections were studied. Twelve patients with HH were identified. The presence of DIC and of PAIgG were often associated with this disease. No herpesvirus infection was demonstrated. Eight of the 12 patients with HH and four of the eight patients without HH died (P = NS). The results of this study suggest that HH could be involved in the development of thrombocytopenia in immunocompetent patients with sepsis syndrome or septic shock. HH does not seem to be associated with increased mortality.