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The mean platelet component (MPC) is a new platelet parameter generated by the Bayer ADVIA 120 full blood count analyser as part of the routine complete blood count (CBC) test cycle. We report a case of myelodysplasia with bleeding complications and abnormal template bleeding time in whom low mean platelet component parameters were associated with partial platelet granule deficiency, demonstrated by transmission electron microscopy. We suggest that the mean platelet component is an inexpensive and rapid test to screen for platelet dysfunction related to ultrastructural abnormalities in myelodysplasia.

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BACKGROUND/AIMS: Thrombocytopenia in chronic liver diseases has traditionally been considered a consequence of platelet pooling and destruction in spleen. We tried to evaluate the influence of thrombopoietin, the physiological regulator of thrombopoiesis, on the origin of this thrombocytopenia. METHODOLOGY: We determined serum thrombopoietin levels by ELISA in thrombocytopenic patients with liver cirrhosis (n = 32) and with chronic hepatitis C viral infection (n = 23). A group of 43 healthy subjects was used as a control. RESULTS: Liver cirrhosis patients presented slightly, but not significantly, lower serum thrombopoietin levels (104 +/- 56 pg/mL) than controls (121 +/- 58 pg/mL) or patients infected with chronic hepatitis C virus (125 +/- 40 pg/mL). No correlations were found between serum thrombopoietin concentrations and liver tests or hematological parameters. CONCLUSIONS: We conclude that low thrombopoietin production may play a role, along with hypersplenism, in the development of thrombocytopenia in patients with liver cirrhosis. Normal thrombopoietin levels exclude a defect in thrombopoietin production as a possible etiology for the thrombocytopenia in patients with chronic hepatitis C viral infection. However, a direct viral megakaryocyte infection or an immune mechanism could explain this thrombocytopenia, according to the thrombopoietin levels detected.

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BACKGROUND AND OBJECTIVE: Exact diagnosis is sometimes difficult in patients presenting with a slight bleeding diathesis, prolonged bleeding times, non-specific aggregometric abnormalities, and/or mild thrombocytopenia. The objective of this study was to evaluate the use of platelet ultrastructural morphometry in detecting a partial d-storage pool disease in such patients. DESIGN AND METHODS: Platelets from 52 patients and 15 controls were fixed immediately in glutaraldehyde in White's saline without anticoagulant and processed for transmission electron microscopy. Using computer-assisted morphometry, the size and shape of the platelets were measured, as were the size and number per platelet of the dense- and a-granules. Ultrastructural morphology of the above and other intraplatelet structures was observed. RESULTS: Twenty-four cases were diagnosed as having a partial d-storage pool disease. Mean platelet area (2.28 microm(2)) and maximum diameter (2.58 microm) were significantly greater in patients than in control subjects (1.64 microm(2) and 2. 25 microm, respectively) but discoid shape was preserved. Mean dense-granule number was decreased, both per platelet and per microm(2) of platelet area (patients 0.22 and 0.09; controls 0.42 and 0.24). Seven patients also had a marked decrease in a-granules, resulting in a significantly lower mean number of granules per microm(2 )(patients 2.43; controls 3.15). Additionally, the patients' platelets had significant increases in both lipid droplets and surface-connected canalicular system. INTERPRETATION AND CONCLUSIONS: A partial dense-granule deficiency, sometimes associated with partial a-granule deficiency, should be borne in mind faced with patients who have a slight bleeding diathesis, non-specific platelet dysfunction tests and/or mild thrombocytopenia of unknown origin. Platelet ultrastructural morphometry is useful in diagnosing this condition.

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Collagen is a powerful platelet activating agent that promotes adhesion and aggregation of platelets. To differentiate the signals generated in these processes we have analyzed the tyrosine phosphorylation occurring in platelets after activation with collagen in suspension or under flow conditions. For the suspension studies, washed platelets were activated with different concentrations of purified type I collagen (ColI). Studies under flow conditions were performed using two different adhesive substrata: ColI and endothelial cells extracellular matrix (ECM). Coverslips coated with ColI or ECM were perfused through a parallel-plate perfusion chamber at 800 s(-1) for 5 min. After activation of platelets either in suspension or by adhesion, samples were solubilized and proteins were resolved by electrophoresis. Tyrosine-phosphorylated proteins were detected in immunoblots by specific antibodies. Activation of platelet suspensions with collagen induced tyrosine phosphorylation before aggregation could be detected. Profiles showing tyrosine-phosphorylated proteins from platelets adhered on ColI or on ECM were almost identical and lacked proteins p95, p80, p66, and p64, which were present in profiles from platelets activated in suspension. The intensity of phosphorylation was quantitatively weaker in those profiles from platelets adhered on ECM. Results from the present work indicate that activation of platelets in suspension or by adhesion induces differential tyrosine phosphorylation patterns. Phosphorylation of proteins p90 and p76 may be related to early activation events occurring during initial contact and spreading of platelets. Considering that adhesion is the first step of platelet activation, studies on signal transduction mechanisms under flow conditions may provide new insights to understand the signaling processes taking place at earliest stages of platelet activation.

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Littoral cell angioma (LCA) is a recently described splenic vascular tumor. We present a new case in a 62-year-old woman with severe thrombocytopenia and mild bleeding diathesis, but without palpable splenomegaly. Abdominal ultrasound and magnetic resonance showed multiple nodular images, suggesting splenic hemangiomas. A platelet kinetic study revealed a very short platelet survival. As the spleen was the site of platelet destruction, splenectomy was carried out. Histopathological and immunohistochemical data allowed a final diagnosis of LCA. Following splenectomy, the patient showed a transitory normalization of the platelet counts. Thrombocytopenia then reappeared but was moderate, without hemorrhagic diathesis. A second platelet kinetic study, performed 16 months post-splenectomy, showed hepatic platelet destruction. However, there were no macroscopic hepatic lesions in a second abdominal magnetic resonance study. This case illustrates the difficulties involved in determining the etiology of many peripheral thrombocytopenias.

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HIV-1 seropositive patients often exhibit thrombocytopenia, considered of multifactorial aetiology. Thrombopoietin (TPO), a recently isolated cytokine, is the main regulator of megakaryocyte and platelet production. The objective of this study was to analyse serum TPO levels in thrombocytopenic and non-thrombocytopenic HIV-1 infected patients. Serum TPO levels were measured by ELISA in 43 healthy individuals and in 88 HIV-1 infected patients: 68 thrombocytopenics and 20 non-thrombocytopenics. Thrombocytopenic HIV-1 infected patients showed higher TPO concentrations (263 +/- 342 pg/ml) than non-thrombocytopenics (191 +/- 86 pg/ml); levels in both groups were significantly higher than those of healthy controls (121 +/- 58 pg/ml). Two subgroups of thrombocytopenic patients, the autoimmune thrombocytopenic purpura (AITP) group and the mild thrombocytopenic group, presented TPO levels similar to those of non-thrombocytopenics. Patients exhibiting pancytopenia showed the highest TPO concentrations. However, there was no correlation between TPO levels and platelet counts in any group of HIV-1 infected patients. TPO levels in HIV-1 seropositive patients were slightly increased and the differences in TPO levels between thrombocytopenic and non-thrombocytopenic patients were generally small. The finding of mildly increased TPO levels along with the recently described recovery of thrombocytopenia following recombinant TPO administration confirms the implication of ineffective platelet production in the origin of HIV-associated thrombocytopenia.

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BACKGROUND AND OBJECTIVE: Thrombocytopenia of peripheral origin is basically due to platelet destruction or splenic sequestration. Thrombopoietin (TPO) regulates platelet production stimulating megakaryocyte proliferation and maturation. The evaluation of TPO levels may be a useful tool in the diagnosis of thrombocytopenias of unknown origin. We tried to determine the value of TPO levels in some thrombocytopenias classically considered as peripheral. DESIGN AND METHODS: Serum TPO levels and platelet counts were measured in 32 thrombocytopenic patients with liver cirrhosis (LC) and 23 with chronic hepatitis C (CHC) viral infection, in 54 patients with a clinical and serological diagnosis of autoimmune thrombocytopenic purpura (AITP), and in 88 patients infected with the human immunodeficiency virus (HIV). RESULTS: Patients with LC, AITP and HIV had lower platelet counts than patients with CHC. The degree of thrombocytopenia did not, however, correlate with the TPO levels. HIV infected patients (246+/-304 pg/mL) and AITP patients (155+/-76 pg/mL) had higher TPO levels than controls (121+/-58 pg/mL). TPO levels in patients with CHC (125+/-40 pg/mL) did not differ from those in control subjects, but were slightly decreased in patients with LC (104+/-56 pg/mL). INTERPRETATION AND CONCLUSIONS: Reduced TPO production could be involved in the development of thrombocytopenia in LC patients, but not in patients with early stages of CHC viral infection. HIV and AITP patients had slightly raised levels of TPO. As TPO levels are normal or slightly increased in most peripheral thrombocytopenias, these data alone are not sufficient to distinguish the different types of peripheral thrombocytopenia. They may, however, be a useful tool for differentiating some central and peripheral thrombocytopenias.

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BACKGROUND AND OBJECTIVE: The distinction between clonal and reactive thrombocytoses is a frequent problem and implies different therapeutic options. As thrombopoietin (TPO) is the main regulator of megakaryocytopoiesis and thrombopoiesis, we measured TPO levels in patients with thrombocytosis in an attempt to understand the regulation and potential utility of distinguishing thrombocytoses. DESIGN AND METHODS: Serum TPO levels, platelet counts, mean platelet volume, hemoglobin, erythrocyte sedimentation rate and age were evaluated in 25 patients with clonal thrombocytosis (15 with essential thrombocythemia, 6 with polycythemia vera and 4 with chronic myeloid leukemia) and in 50 patients with reactive thrombocytosis distributed in three groups: 1) patients in post-surgical states; 2) patients with solid tumors; and 3) patients with inflammatory diseases. RESULTS: TPO levels were slightly increased in patients with clonal (135+/-50 pg/mL) and reactive (147+/-58 pg/mL) thrombocytosis compared with controls (121+/-58 pg/mL). Analyzing the different groups, patients with essential thrombocythemia had the lowest TPO levels (120+/-28 pg/mL) and patients with solid tumors the highest levels (162+/-59 pg/mL). Patients with clonal thrombocytosis were older, had higher platelet counts, mean platelet volume and hemoglobin, and lower erythrocyte sedimentation rate than patients with reactive thrombocytosis. INTERPRETATION AND CONCLUSIONS: Minor differences were observed in TPO levels between patients with primary and secondary thrombocytoses. Erythrocyte sedimentation rate, but not TPO levels, may be a useful tool for discriminating both types of thrombocytoses.

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Formestane is a new aromatase inhibitor used as second-line endocrine treatment for postmenopausal women with advanced breast cancer. The most frequent side effects are local reactions. Here we report the development of immune thrombocytopenia coinciding with administration of this drug.

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A case of type IV Ehlers-Danlos syndrome with a partial platelet delta-storage pool disease is reported. The diagnosis of Ehlers-Danlos was clinical. The platelet-dense granule deficiency was determined by ultrastructural platelet morphology. Dense bodies were decreased in number, and most showed loss or fragmentation of electron-dense material. Aggregation studies revealed a retarded response to ristocetin and arachidonic acid, which was corrected with desmopressin acetate-DDAVP.

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The appearance of "giant perichromatin granules" to date has been considered pathognomonic of nasopharyngeal angiofibroma. We present the finding of giant intranuclear granules in human megakaryocytes. The patient was a 34-year-old woman with a diagnosis of Sebastian platelet syndrome. The bone marrow aspirate showed an increased number of megakaryocytes. Ultrastructural study revealed giant perichromatin-like granules in the nuclei of 80% megakaryocytes. These granules were round or oval and size ranged 230 to 540 nm. Further studies are needed in our patient to determine the significance of these granules.

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BACKGROUND: We analyze the etiopathogenesis and clinical and immunohematological characteristics of 60 pregnant women with isolated thrombocytopenia (TP) (platelet count < 150 x 10(9)/l); and the frequency of TP and hemorrhagic complications in their newborn. We suggest the therapeutic approach for each maternal TP type. PATIENTS AND METHODS: We performed: clinical history, platelet count (EDTA K3, sodium citrate, microscopic exam) and investigation of antiplatelet antibodies (immunofluorescence) in all pregnant women. A familial history and ultrastructure of platelets were studied when hereditary macrothrombocytopenia (HM) was suspected. A Levine's test of homogenicity of variances was applied to compare the mean platelet count in each diagnostic group. A linear regression between maternal and newborn platelet counts was performed. RESULTS: In 37 thrombocytopenic women (62%) no antiplatelet antibodies were found, and the clinical history was negative for previous TP or abnormal bleeding. Four patients (7%) were diagnosed as pseudothrombocytopenia EDTA-mediated, and eight (13%) of HM. Finally, an autoimmune etiology was suspected in 11 women (18%) and antiplatelet antibodies were detected in 9. Mean platelet counts of mother with immune TP did not show statistically significant differences with other diagnostic groups. Abnormal bleeding was not observed in any patient or newborn. There was no correlation between platelet counts of mothers and newborns. Platelet count obtained by skull bone punction led to unnecessary caesarians in four cases. CONCLUSIONS: The frequency of immune thrombocytopenia in pregnant women is low (18%). There is a high prevalence of benign TP (62%). The pseudothrombocytopenias and HM are frequent findings (20%), and special care is advisable in these cases to avoid unnecessary therapeutic procedures.

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INTRODUCTION: Hereditary macrothrombocytopenias (HM) are a group of infrequent disorders characterized by hereditary giant platelets. Little has been published about the course of these diseases during pregnancy and delivery. SUBJECTS AND METHODS: Forty consecutive thrombocytopenic pregnant women were studied. Platelet count, mean platelet volume and blood smear examination were performed. Platelet antibodies were studied by immunofluorescence. Familial study, bleeding time, ultrastructural platelet examination, a von Willebrand disease screening and aggregation tests were carried out when HM was suspected. RESULTS: Four cases of HM were diagnosed. Giant platelets were observed in all cases, with the typical ultrastructural pattern. Döhle-like cytoplasmic inclusions in granulocytes were observed in one case. Platelet antibodies were detected in only one case. No prophylactic measures to prevent haemorrhage were adopted, and all patients underwent vaginal deliveries. Haemorrhagic events were absent in both mothers and children. CONCLUSIONS: The prevalence of HM in pregnant trombocytopenic women is higher than assumed. Prophylactic treatment should be avoided in the absence of a history of haemorrhagic complications and obstetrical risk factors.

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Cryptic antigens are detected by antibodies present in a wide spectrum of patients with or without thrombocytopenia, and even in healthy individuals. They are produced for unknown reasons and do not react with antigens of native platelets, but only with altered platelets. Cryptantigen antibodies may not only result in spuriously low platelet counts, but also in 'falsely' positive tests for platelet antibodies. We report our experience in the characterization of the different types of antibodies directed against cryptantigens of platelets: EDTA-dependent antibodies, PFA-dependent antibodies, EDTA-PFA-dependent antibodies and cold agglutinins. These antibodies were detected in the course of the serological study of 37 patients from a group of 356 (10%) whose blood was sent to our laboratory for platelet antibody testing. Pseudothrombocytopenia was diagnosed in 24 cases. Twenty-one of these showed EDTA-dependent or EDTA-PFA-dependent platelet agglutination and three were due to the presence of cold agglutinins. In 13 patients the thrombocytopenia was genuine. Eleven of these presented EDTA-dependent or EDTA-PFA-dependent antibodies in their serum and in the two remaining cases PFA-dependent antibodies were found. Cryptantigen antibodies were also detected in 9 out of 228 (4%) blood donors who were used as healthy controls in the platelet immunofluorescence test. In the light of the results obtained we put forward some guidelines to detect the presence of these antibodies and establish an accurate serological and clinical diagnosis of the autoimmune thrombocytopenias.

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BACKGROUND: The immunologic study of 60 intravenous drug addict patients who were seropositive for the human immunodeficiency virus (HIV) and who developed thrombocytopenia (TP) is reported with the aim of establishing the relation of possible pathogenic factors which may trigger this complication. METHODS: In all the patients the presence of antiplatelet antibodies was studied by direct and indirect immunofluorescence together with crypto-antibodies, immune complexes, lymphocytotoxic antibodies, antiphospholipid antibodies, immunoglobulins, lymphocytic populations and subpopulations and serology against different infectious agents. RESULTS: Antiplatelet antibodies were detected in 71% of the patients of which 50% corresponded to immunoglobulins of IgG class, 12% to IgM, 21% to IgG plus IgM, 7% IgM plus IgA, 5% to IgG plus IgA and 5% IgG plus IgM plus IgA. In these patients a characteristic membrane fluorescence pattern was observed in which the fluorescein is distributed forming a thick, hard point. In 3 patients EDTA dependent crypto-antibodies were detected which in one case determined pseudothrombocytopenia. The immune complexes were demonstrated in 50% of the cases. Other findings were: hypergammaglobulinemia (86%), decrease in the CD4 population (47%), CD4/CD8 ratio < 1 (71%), lymphocytotoxic antibodies (70%), antiphospholipid antibodies (60%), and seropositivity for cytomegalovirus (62%), Epstein-Barr virus (10%) and hepatitis B virus (anti-HBc 75%, HBsAg 33%). CONCLUSIONS: Thrombocytopenia associated to infection by the human immunodeficiency virus in intravenous drug addict patients is due to the concurrence of multiple factors. The relevance of each may vary according to the risk practice of the collective analysed and even within the same group of some individuals or others. The numerous serologic findings in these patients fundamentally express the existence of a chronic polyclonal stimulation of B cells which may be initiated by the action of the drug itself and which becomes aggravated during the course of the multiple acquired infections among which that due to the human immunodeficiency virus is of note.

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