Cross-reactivity between erythropoietin and thrombopoietin at the level of Mpl does not account for the thrombocytosis seen in iron deficiency

Trace Metals and The Hemostatic System

In this narrative review we report the main relationships between trace metals and the hemostatic system since this aspect has seldom attracted the attention of the scientific community. A basic aspect to be considered is the importance of maintaining the fine control of all trace metals' levels since they have an important impact on the pathophysiology of the hemostatic system. It is worth noting that poor diet habits are responsible for most trace metal deficiencies, while pollution is responsible for dangerous exposure to them with a consequent negative impact on the general population. This appears of paramount importance in planning the implementation of food and nutrient support to ameliorate the hidden hunger and the quality of life of people especially in developing countries and limiting poisons both in the air and food. As it often happens, when damage to certain mechanisms takes a very long time to appear, no attention is paid to the importance of a systematic prevention to avoid late negative outcomes.

Thrombocytopenia in severe iron deficiency anemia in children

AIM

Iron deficiency anemia (IDA) is common in the pediatric population and often accompanied by mild thrombocytosis, but rarely profound thrombocytopenia is seen. We describe the data of children with IDA and thrombocytopenia in two centers and discuss the published data in the literature.

METHODS

In this retrospective case series, the medical records of patients under the age of 19 years old diagnosed with IDA in two tertiary medical centers over the last 10 years, were reviewed. The data were collected and compared to the data published in the medical literature.

RESULTS

All the patients presented with severe IDA and thrombocytopenia improved with iron treatment. Although none of the patients had signs of major bleeding, the thrombocytopenia could mostly be classified as severe (platelet count <50×10E9/L). Due to the severity of the anemia, in about half of the cases, a red blood cell transfusion was given. The peak of the platelet count was seen in the first month after the start of iron treatment. In eight cases of children with IDA, the thrombocytopenia appeared after the supplementation of iron was started.

CONCLUSION

Clinically stable children with severe IDA and thrombocytopenia, where other causes are very unlikely, warrant an empiric monotherapy with iron to prevent unnecessary investigations and treatments.

Complex Interactions in Regulation of Haematopoiesis-An Unexplored Iron Mine

Iron is one of the most abundant metals on earth and is vital for the growth and survival of life forms. It is crucial for the functioning of plants and animals as it is an integral component of the photosynthetic apparatus and innumerable proteins and enzymes. It plays a pivotal role in haematopoiesis and affects the development and differentiation of different haematopoietic lineages, apart from its obvious necessity in erythropoiesis. A large amount of iron stores in humans is diverted towards the latter process, as iron is an indispensable component of haemoglobin. This review summarises the important players of iron metabolism and homeostasis that have been discovered in recent years and highlights the overall significance of iron in haematopoiesis. Its role in maintenance of haematopoietic stem cells, influence on differentiation of varied haematopoietic lineages and consequences of iron deficiency/overloading on development and maturation of different groups of haematopoietic cells have been discussed.

Low iron promotes megakaryocytic commitment of megakaryocytic-erythroid progenitors in humans and mice

The mechanisms underlying thrombocytosis in patients with iron deficiency anemia remain unknown. Here, we present findings that support the hypothesis that low iron biases the commitment of megakaryocytic (Mk)-erythroid progenitors (MEPs) toward the Mk lineage in both human and mouse. In MEPs of transmembrane serine protease 6 knockout (Tmprss6-/-) mice, which exhibit iron deficiency anemia and thrombocytosis, we observed a Mk bias, decreased labile iron, and decreased proliferation relative to wild-type (WT) MEPs. Bone marrow transplantation assays suggest that systemic iron deficiency, rather than a local role for Tmprss6-/- in hematopoietic cells, contributes to the MEP lineage commitment bias observed in Tmprss6-/- mice. Nontransgenic mice with acquired iron deficiency anemia also show thrombocytosis and Mk-biased MEPs. Gene expression analysis reveals that messenger RNAs encoding genes involved in metabolic, vascular endothelial growth factor, and extracellular signal-regulated kinase (ERK) pathways are enriched in Tmprss6-/- vs WT MEPs. Corroborating our findings from the murine models of iron deficiency anemia, primary human MEPs exhibit decreased proliferation and Mk-biased commitment after knockdown of transferrin receptor 2, a putative iron sensor. Signal transduction analyses reveal that both human and murine MEP have lower levels of phospho-ERK1/2 in iron-deficient conditions compared with controls. These data are consistent with a model in which low iron in the marrow environment affects MEP metabolism, attenuates ERK signaling, slows proliferation, and biases MEPs toward Mk lineage commitment.

Thrombocytosis in 715 Dogs (2011-2015)

BACKGROUND

Thrombocytosis is a hematologic abnormality in dogs that has been associated with various neoplastic, metabolic, and inflammatory conditions.

OBJECTIVE

To classify thrombocytosis in dogs based on severity and evaluate whether there are associations between severity and underlying disease processes.

ANIMALS

Seven hundred and fifteen dogs with thrombocytosis and 1,430 dogs with normal numbers of platelets.

METHODS

Retrospective study. Medical records of dogs with increased (>500 × 10³ /μL; thrombocytosis group) and normal (300-500 × 10³ /μL; control group) platelet counts between 2011 and 2015 were reviewed. Dogs were characterized by severity of platelet increase and diagnosis. Diagnostic categories included neoplasia, endocrine disease, inflammatory disease, or miscellaneous.

RESULTS

A total of 1,254 complete blood counts with thrombocytosis from 715 dogs were included in the study. Median platelet count in this population was 582 × 10³ /μL (500-1,810 × 10³ /μL). No correlation between severity of thrombocytosis and diagnosis was identified. Causes of secondary thrombocytosis included neoplasia (55.7%), endocrine disease (12.0%), and inflammatory disease (46.6%). Immune-mediated disease was common (22.2%), associated with frequent glucocorticoid administration, and had a significantly higher median platelet count (636 × 10³ /μL [500-1,262 × 10³ /μL] versus 565 × 10³ /μL [500-1,810 × 10³ /μL]) when compared to the other inflammatory processes (P < 0.001). The diagnoses in the thrombocytosis dogs differed significantly from the control population (P < 0.001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Thrombocytosis is commonly associated with carcinoma and immune-mediated disease in dogs.

Prevalence of Factor V Leiden-G1691A and MTHFR-C677T Thrombosis Gene Modifier in Iron Deficiency Anemia: A Pathophysiological Effect in Indian Isolates

Normal iron levels are required to prevent thrombocytosis by inhibiting thrombopoiesis. Thrombocytosis is usually associated with a mild iron deficiency and is the result of a lack of inhibition of thrombopoiesis. Study participants were 430 iron deficiency anemia (IDA) patients. Ten (10) mL of venous blood were collected for the subjects. Ferritin analysis was done by ELISA method while Hemogram analysis was done by auto-analyzer. Factor V Leiden, PRTG20210A, and MTHFR C677T genotype analysis was performed by PCR-RFLP method. Among the patients, 9 were heterozygous (G>A) and 2 were homozygous (A>A) carrier of FV Leiden; while 20 were heterozygous (C>T) and 3 were homozygous (T>T) for MTHFR polymorphism. None of the patient was identified with PT mutation. Patients with thrombosis gene marker had lower hemoglobin, mean corpuscular volume, mean corpuscular haemoglobin levels, and mean corpuscular hemoglobin concentration than patients without thrombosis gene marker. Serum ferritin was elevated in subject with the absence of thrombosis gene markers. Our data suggest a high impact of inherited hypercoagulability risk factors in the pathogenesis of IDA and its complications.

[Iron deficiency, thrombocytosis and thromboembolism]

Iron deficiency, the most common nutritional deficiency worldwide, is often associated with reactive thrombocytosis. Although secondary thrombocytosis is commonly considered to be harmless, there is accumulating evidence that elevated platelet counts, especially in the setting of iron deficiency, can lead to an increased thromboembolic risk in both arterial and venous systems. Here we present the mechanisms of iron deficiency-induced thrombocytosis and summarize its clinical consequences especially in patients with inflammatory bowel diseases, chronic kidney disease or cancer. We hypothesize that iron deficiency is an underestimated thromboembolic risk factor, and that iron replacement therapy can become an effective preventive strategy in a variety of clinical settings.

The pathophysiology of thrombocytopenia in chronic liver disease

Thrombocytopenia is the most common hematological abnormality encountered in patients with chronic liver disease (CLD). In addition to being an indicator of advanced disease and poor prognosis, it frequently prevents crucial interventions. Historically, thrombocytopenia has been attributed to hypersplenism, which is the increased pooling of platelets in a spleen enlarged by congestive splenomegaly secondary to portal hypertension. Over the past decade, however, there have been significant advances in the understanding of thrombopoiesis, which, in turn, has led to an improved understanding of thrombocytopenia in cirrhosis. Multiple factors contribute to the development of thrombocytopenia and these can broadly be divided into those that cause decreased production, splenic sequestration, and increased destruction. Depressed thrombopoietin levels in CLD, together with direct bone marrow suppression, result in a reduced rate of platelet production. Thrombopoietin regulates both platelet production and maturation and is impaired in CLD. Bone marrow suppression can be caused by viruses, alcohol, iron overload, and medications. Splenic sequestration results from hypersplenism. The increased rate of platelet destruction in cirrhosis also occurs through a number of pathways: increased shear stress, increased fibrinolysis, bacterial translocation, and infection result in an increased rate of platelet aggregation, while autoimmune disease and raised titers of antiplatelet immunoglobulin result in the immunologic destruction of platelets. An in-depth understanding of the complex pathophysiology of the thrombocytopenia of CLD is crucial when considering treatment strategies. This review outlines the recent advances in our understanding of thrombocytopenia in cirrhosis and CLD.

Primary thrombocytosis in children

Myeloproliferative neoplasms are uncommon disorders in children, for which we have limited understanding of the pathogenesis and optimal management. JAK2 and MPL mutations, while common drivers of myeloproliferative neoplasms in adult patients, are not clearly linked to pediatric disease. Management and clinical outcomes in adults have been well delineated with defined recommendations for risk stratification and treatment. This is not the case for pediatric patients, for whom there is neither a standard approach to workup nor any consensus regarding management. This review will discuss thrombocytosis in children, including causes of thrombocytosis in children, the limited knowledge we have regarding pediatric primary thrombocytosis, and our thoughts on potential risk stratification and management, and future questions to be answered by laboratory research and collaborative clinical study.

Iron deficiency alters megakaryopoiesis and platelet phenotype independent of thrombopoietin

Iron deficiency is a common cause of reactive thrombocytosis, however, the exact pathways have not been revealed. Here we aimed to study the mechanisms behind iron deficiency‐induced thrombocytosis. Within few weeks, iron‐depleted diet caused iron deficiency in young Sprague–Dawley rats, as reflected by a drop in hemoglobin, mean corpuscular volume, hepatic iron content and hepcidin mRNA in the liver. Thrombocytosis established in parallel. Moreover, platelets produced in iron deficient animals displayed a higher mean platelet volume and increased aggregation. Bone marrow studies revealed subtle alterations that are suggestive of expansion of megakaryocyte progenitors, an increase in megakaryocyte ploidy and accelerated megakaryocyte differentiation. Iron deficiency did not alter the production of hematopoietic growth factors such as thrombopoietin, interleukin 6 or interleukin 11. Megakaryocytic cell lines grown in iron‐depleted conditions exhibited reduced proliferation but increased ploidy and cell size. Our data suggest that iron deficiency increases megakaryopoietic differentiation and alters platelet phenotype without changes in megakaryocyte growth factors, specifically TPO. Iron deficiency‐induced thrombocytosis may have evolved to maintain or increase the coagulation capacity in conditions with chronic bleeding. Am. J. Hematol. 89:524–529, 2014. © 2014 Wiley Periodicals, Inc.

Iron deficiency anemia as a risk factor for cerebrovascular events in early childhood: a case-control study

In recent years, iron-deficiency anemia (IDA) has been suggested to have an association with childhood-onset ischemic stroke in otherwise healthy children, but few cases have proven it thus far. In this study, we aimed to investigate whether iron-deficiency anemia is a risk factor for cerebrovascular events and childhood-onset ischemic stroke in previously healthy children. This was a case-control study that included 21 stroke cases with patients who had previously been generally healthy, and matched with age and gender of 100 healthy control subjects. Patients were included if a diagnosis of definite stroke had been made and other known etiologies of childhood onset stroke were excluded. For all subjects, iron parameters including serum iron, ferritin, transferrin, total iron binding capacity, and transferrin saturation were assessed. We screened all case patients for prothrombotic factors including level of hemoglobin S, protein C, protein S, antithrombin III, lupus anticoagulant, factor V Leiden, and prothrombin gene mutation (G20210A). Brain magnetic resonance images (MRI), magnetic resonance angiography (MRA), and magnetic resonance venography (MRV) were performed to all case patients. All case patients have normal results regarding functional, immunological, and molecular assay for prothrombotic factors screening. Our results showed that IDA was disclosed in 57.1 % of stroke cases with no identified cause, as compared to 26 % of controls. Our study suggest that previously healthy children who developed stroke are 3.8 times more likely to have IDA than healthy children, who do not develop stroke (OR, 3.8; 95 % CI:1.3-11.2 P = 0.005). In addition, there was significant interaction between IDA and thrombocytosis among studied cases (OR, 10.5; 95 % CI, 1.0-152 P = 0.02). There were nonsignificant differences between stroke patients with IDA and those with normal iron parameters regarding stroke subtype (P > 0.05). Public health messages on the importance of early detection of iron-deficiency anemia in young children, especially in our developing countries so that it can be treated before a life-threatening complication like stroke develops.

Severe thrombocytopenia with iron deficiency anemia

Although severe thrombocytopenia has been reported among children with iron deficiency anemia, the presence of both anemia and thrombocytopenia can suggest serious or malignant bone marrow dysfunction, requiring further work-up. This paper reviews the management and outcomes of patients with the diagnosis of iron deficiency anemia presenting with severe thrombocytopenia. The authors present 4 pediatric patients with iron deficiency anemia and severe thrombocytopenia at initial presentation. Charts were reviewed after approval by the institutional review boards at both St. Jude Children's Research Hospital and LeBonheur Children's Medical Center in Memphis, Tennessee. All 4 patients' hemoglobin concentrations and platelet counts normalized within 1 to 3 weeks of initiating iron supplementation, suggesting that in such patients iron supplementation can obviate the need for invasive diagnostic procedures. In addition, these patients all had a platelet "overshoot" phenomenon during iron therapy prior to normalization of platelet counts, the mechanism of which is still unknown. The literature exploring the mechanism behind the current clinical findings is reviewed.

Iron and thrombosis

Although essential for cell physiology, an increase or depletion of body iron has harmful effects on health. Apart from iron deficiency anemia and iron overload-related organ tissue damage, there are increasing evidences that body iron status is implicated in atherosclerotic cardiovascular diseases. The hypothesis formulated in 1981 that iron depletion may protect against cardiovascular events is intriguing and has generated a significant debate in the last two decades. Indeed, to study this phenomenon, several investigators have tried to design appropriate experimental and clinical studies and to identify useful biochemical and genetic markers of iron status. The results of the literature on the effect of iron deficiency and overload on vascular health are critically reviewed in this study from a pathogenic and clinical point of view.

[Thrombocytosis and essential thrombocythemia in childhood]

Thrombocytosis is frequently observed in pediatric patients. Among them the secondary thrombocytosis are the most frequent and result from several causes. The rarely primary thrombocytosis can be either constitutive (and often familial) or acquired (essential thrombocythemia). The purpose of this article is to give diagnostic orientation and to suggest which biological tests should be performed.

Primary and secondary thrombocytosis in childhood

This review summarizes current data on the pathomechanisms and clinical aspects of primary and secondary thrombocytosis in childhood. Primary thrombocytosis is extremely rare in childhood, mostly diagnosed at the beginning of the second decade of life. As in adults, the criteria of the Polycythemia Vera Group are appropriate to diagnose primary thrombocytosis. The pathomechansims of non-familial forms are complex and include spontaneous formation of megakaryopoietic progenitors and increased sensitivity to thrombopoietin (Tpo). Familial forms can be caused by mutations in Tpo or Tpo receptor (c-mpl) genes. These mutations result in overexpression of Tpo, sustained intracellular signalling or disturbed regulation of circulating Tpo. Treatment of primary thrombocytosis is not recommended if platelet counts are <1500/nl and bleeding or thrombosis did not occur in patient's history. In severe cases, decision on treatment should weigh potential risks of treatment options (hydroxyurea, anagrelide) against expected benefits for preventing thrombosis or haemorrhage. Secondary thrombocytosis is frequent in children, in particular in the first decade of life. Hepatic Tpo production is stimulated in acute response reaction to a variety of disorders. Thrombosis prophylaxis is not required, even at platelet counts >1000/nl, except for cases with additional prothrombotic risk factors.