Thrombocytopenia in the neonate

Identification of a potent small molecule capable of regulating polyploidization, megakaryocyte maturation, and platelet production

Background

Megakaryocytic cell maturation involves polyploidization, and megakaryocyte (MK) ploidy correlates with their maturation and platelet production. Retardation of MK maturation is closely associated with poor MK engraftment after cord blood transplantation and neonatal thrombocytopenia. Despite the high prevalence of thrombocytopenia in a range of setting that affect infants to adults, there are still very limited modalities of treatment.

Methods

Human CD34⁺ cells were isolated from cord blood or bone marrow samples acquired from consenting patients. Cells were cultured and induced using 616452 and compared to current drugs on the market such as rominplostim or TPO. Ploidy analysis was completed using propidium iodide staining and flow cytometry analysis. Animal studies consisted of transplanting human CD34⁺ cells into NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ mice followed by daily injections of 15 mg/kg of 616452.

Results

Within one week of culture, the chemical was able to induce polyploidization, the process required for megakaryocyte maturation with the accumulation of DNA content, to 64 N or greater to achieve a relative adult size. We observed fold increases as high as 200-fold in cells of 16 N or greater compared to un-induced cells with a dose-dependent manner. In addition, MK differentiated in the presence of 616452 demonstrated a more robust capacity of MK differentiation than that of MKs cultured with rominplostim used for adult idiopathic thrombocytopenic purpura (ITP) patients. In mice transplanted with human cord blood, 616452 strikingly enhanced MK reconstitution in the marrow and human peripheral platelet production. The molecular therapeutic actions for this chemical may be through TPO-independent pathways.

Conclusion

Our studies may have an important impact on our fundamental understanding of fetal MK biology, the clinical management of thrombocytopenic neonates and leukemic differentiation therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0358-y) contains supplementary material, which is available to authorized users.

Organism-specific platelet response and factors affecting survival in thrombocytopenic very low birth weight babies with sepsis

OBJECTIVE

To study organism-specific platelet response and factors affecting survival in thrombocytopenic very low birth weight (VLBW) babies with sepsis.

STUDY DESIGN

Very low birth weight babies (birth weight <1500 g) admitted to a single level-three intensive care unit from January 2000 to December 2005 were prospectively evaluated for sepsis by rapid screen test, blood counts and blood culture. In thrombocytopenic babies, organism-specific platelet response and its effect on various platelet parameters were evaluated. In addition, morbidity, mortality and factors affecting survival were studied.

RESULT

Sepsis was diagnosed in 230 of 620 (37%) patients. Gram-positive sepsis occurred in 20% (46/230), Gram-negative in 71% (164/230) and fungal in 8.6% (20/230) of patients. Thrombocytopenia was observed in 67% (155/230) of babies. The frequency and duration of thrombocytopenia were more with Gram-negative and fungal infections. The incidence of persistent bacteremia, multiorgan failure and death was more in thrombocytopenic neonates (P<0.01). The incidence of multiorgan failure and death was directly related to the duration of thrombocytopenia. On multiple logistic regression analysis, poor prognostic factors include a high SNAP score at admission, a severe drop in platelet count at onset of sepsis, a low platelet nadir, a prolonged duration of thrombocytopenia, a need for platelet transfusion, less number of days off ventilation and a prolonged stay in the hospital.

CONCLUSION

In thrombocytopenic VLBW babies with sepsis, organism-specific platelet response is seen. In addition, persistent bacteremia, multiorgan failure and death are more in these babies, and survival decreases with the increased severity and duration of thrombocytopenia, with prolonged ventilation and increased need for platelet transfusions.

Mean platelet volume in neonatal respiratory distress syndrome

The aim of this study was to investigate the differences in mean platelet volume (MPV) between neonates with and without neonatal respiratory distress syndrome (RDS). Eighty-three premature infants who were admitted to the neonatal intensive care unit were included in the study. Forty-four of these infants were diagnosed as having RDS and the other 39 infants were non-RDS patients. Infants born to mothers with pre-eclampsia, or a drug history that had negative effects on platelet count, perinatal hypoxia, sepsis and necrotizing enterocolitis were excluded. Blood collection was done on the first and third days of life. There were no demographic, gestational or platelet count differences between groups, but MPV was higher in RDS patients and this difference was statistically significant (P= 0.011). High platelet volumes in RDS patients is probably related to young platelet production and may be a result of increased platelet consumption in pulmonary damage due to RDS.

A prospective study on the prevalence and risk factors for neonatal thrombocytopenia and platelet alloimmunization among 9332 unselected Brazilian newborns

BACKGROUND

Neonatal thrombocytopenia (NT) occurs in 0.5 to 0.9% of unselected Caucasian newborns. However, the prevalence of this complication in other populations is unknown. In this study the prevalence/causes of NT was determined in Brazilian newborns, a population characterized by admixture among Indigenous, Africans, and Caucasians.

STUDY DESIGN

A prospective study was carried out in a 3-year period, to determine the prevalence and causes of thrombocytopenia in cord blood samples. Genotyping for HPA 1-5 systems was performed in pairs of mother/neonates with and without thrombocytopenia. All mothers with genotypic mismatches from each group were tested for HPA-specific antibody using the MAIPA technique to identify alloimmunization.

RESULTS

Platelet counts <100 x 10(9)/L were detected in 1.5% of 9,332 unselected newborns. In 0.15%, platelet count was <50 x 10(9)/L. Clinically significant bleeding was rare. Underlying diseases were present in 48% of the thrombocytopenic cases. HPA 1-5 system genotype mismatches occurred in 50% of gestations, but did not predict the risk for thrombocytopenia. Notably, mismatched genotypes for HPA-5 were slightly increased in the thrombocytopenic group. The presence of anti-HPA-5b antibodies was observed in 0.05% of unselected pregnancies, but increased to 12% among mothers of neonates with thrombocytopenia and mismatched genotype (N = 51).

CONCLUSIONS

Neonatal thrombocytopenia is common among Brazilian newborns at rates comparable with those described among Caucasians. These data suggest that screening for genotypic HPA mismatch, followed by an HPA-specific immunoassay system, particularly for the HPA-5 system, among mothers of newborns with thrombocytopenia in our population would allow the identification of pregnancies at risk of alloimmune thrombocytopenia.

Neonatal thrombocytopenia: causes and management

Neonatal thrombocytopenia is a common clinical problem. Thrombocytopenia presenting in the first 72 hours of life is usually secondary to placental insufficiency and caused by reduced platelet production; fortunately most episodes are mild or moderate and resolve spontaneously. Thrombocytopenia presenting after 72 hours of age is usually secondary to sepsis or necrotising enterocolitis and is usually more severe and prolonged. Platelet transfusion remains the only treatment. There is a need for trials to define the safe lower limit for platelet count and which neonates will benefit from treatment.

Platelet count and sepsis in very low birth weight neonates: is there an organism-specific response?

OBJECTIVE

Thrombocytopenia is commonly observed in very low birth weight (VLBW) neonates with sepsis. Specific platelet responses to different infectious agents have not been extensively characterized. The objectives of this study were to examine platelet counts and platelet indices in preterm neonates with culture-proven sepsis to determine if there are organism-specific platelet responses.

STUDY DESIGN

We analyzed a cohort of all VLBW neonates (birthweight <1500 g) born over a 4-year period and admitted to a single level III neonatal intensive care unit (N = 943). Thrombocytopenia was defined as a platelet count <100,000/mm(3). Platelet count, nadir, duration of thrombocytopenia, and mean platelet volume (MPV) were examined during episodes of culture-proven sepsis. Analysis of variance, Kruskal-Wallis, Mann-Whitney U, and chi(2) tests were used to compare groups, and data are expressed as mean +/- standard deviation.

RESULTS

Sepsis was diagnosed in 154 (16%) of 943 patients in the study population. Of the sepsis episodes, 54% were associated with thrombocytopenia and 61% with an elevation in MPV. Infections were grouped by organism type: Gram-positive bacteria (117/154, 76%), Gram-negative bacteria (24/154, 16%), and fungi (13/154, 8%). When compared with patients with Gram-positive sepsis, those with Gram-negative or fungal sepsis had a significantly lower initial platelet count, a lower platelet nadir, a higher incidence of thrombocytopenia, and a greater duration of thrombocytopenia. The decrease in platelet count from baseline was also significantly less in the Gram-positive infections than in the fungal infections. Although there was an overall increase in MPV from baseline, there were no differences between groups.

CONCLUSIONS

In our population of VLBW infants, sepsis is frequently associated with thrombocytopenia and an elevation in MPV. However, fungal and Gram-negative pathogens are associated with a lower platelet count and more prolonged thrombocytopenia compared with Gram-positive pathogens. We conclude that common pathogens causing sepsis have different effects on platelet kinetics.

Cervical spinal cord hemorrhage secondary to neonatal alloimmune thrombocytopenia

Neonatal alloimmune thrombocytopenia with intracranial hemorrhage is a reported phenomenon. While most of the hemorrhages are noted to be either intraventricular or intraparenchymal, the authors describe the case of a fourth-ventricle hemorrhage with extension into the spinal column down the cervical spinal cord secondary to maternal anti-human platelet antigen (HPA-1a) antibody.

Evaluation and treatment of thrombocytopenia in the neonatal intensive care unit

Phlebotomy-induced anaemia excepted, thrombocytopenia is the most common haematological abnormality in neonatal intensive care unit (NICU) patients. Roughly one-quarter of all NICU patients and half of all sick preterm neonates develop thrombocytopenia. Whereas a large number of varied precipitating conditions has been identified, early-onset thrombocytopenia (<72 h) is most commonly associated with fetomaternal conditions complicated by placental insufficiency and/or fetal hypoxia, e.g. maternal pre-eclampsia and fetal intrauterine growth restriction. The resulting neonatal thrombocytopenia is usually mild to moderate, resolves spontaneously and requires no specific therapy. Deviation from this pattern of thrombocytopenia suggests the presence of more significant precipitating conditions. The most important of these are the immune thrombocytopenias, and every NICU should develop investigation and treatment protocols to manage these cases promptly and avoid unnecessary risk of haemorrhage. In contrast, late-onset thrombocytopenia (>72 h) is almost always associated with sepsis or necrotizing enterocolitis and the associated thrombocytopenia is severe, prolonged and often requires treatment by platelet transfusion. Unfortunately, evidence-based guidelines for platelet transfusion therapy in NICU patients are currently unavailable, making it difficult to define widely accepted thresholds for transfusion and leading to a significant variation in transfusion practice between centres.

CONCLUSION

While improving this situation remains a pressing need, the growing evidence that impaired megakaryocytopoiesis and platelet production are major contributors to many neonatal thrombocytopenias suggests that recombinant haemopoietic growth factors, including thrombopoietin and interleukin-11, may be useful future therapies to ameliorate neonatal thrombocytopenia.

Thrombocytopenia in the newborn

Thrombocytopenia remains a common problem in sick newborns. A quarter of all neonates admitted to neonatal intensive care units develop thrombocytopenia, and in 20% of episodes the thrombocytopenia is severe (platelets <50 x 10(9)/L). Practical and clinically relevant classifications of neonatal thrombocytopenia have now been developed which, by highlighting the principal conditions precipitating severe thrombocytopenia (eg, sepsis, necrotizing enterocolitis, perinatal asphyxia, and the immune thrombocytopenias), aid the practicing neonatologist. Recent reviews demonstrate that many neonates with severe thrombocytopenia receive repeated platelet transfusions, although evidence of their clinical benefit is lacking, and there exists a significant variation in platelet transfusion practice between centers. These facts support the need for the development of evidence-based protocols for platelet transfusion in the newborn and stimulate continued interest in the potential of hemopoietic growth factors (, thrombopoietin and interleukin-11) to prevent or treat neonatal thrombocytopenia.

Epidemiologic and outcome studies of patients who received platelet transfusions in the neonatal intensive care unit

STUDY DESIGN

We conducted a historic cohort study of neonates who received platelet transfusions at the National Institute of Perinatology, Mexico City, from January 1997 to May 2000. We obtained descriptive and outcome data, and assessed demographic and laboratory means of predicting "good candidates" for a future recombinant thrombopoietin (rTpo) trial.

RESULTS

A minority of the transfused patients (11.4%) received only one transfusion; the majority (88.6%) received multiple transfusions. Neonates who received one or more platelet transfusions were more likely to die (24.5% mortality) than neonates who received no platelet transfusions (3.7% mortality). Regression analyses indicated that the presence of liver disease was the best predictor of a "good candidate" for rTpo administration.

CONCLUSION

The majority of neonates in our institution who receive platelet transfusions receive multiple, not single, transfusions. Receiving any platelet transfusion is a marker for high risk of death. Neonates with liver disease who receive platelet transfusions might be a reasonable group for a phase I rTpo trial.

Association between serum macrophage colony-stimulating factor levels and monocyte and thrombocyte counts in healthy, hypoxic, and septic term neonates

OBJECTIVE

Macrophage colony-stimulating factor (M-CSF) is a hematopoietic growth factor that mainly stimulates the growth, differentiation, and proliferation of cells of the monocyte-macrophage lineage. There are only limited numbers of studies about M-CSF levels in neonates, but high levels of serum M-CSF have been reported in septic and some thrombocytopenic adult patients. In this study, we investigated the serum M-CSF levels in healthy, septic, and hypoxic term neonates on the first day of life and examined the relationship of serum M-CSF levels and circulating monocyte and thrombocyte counts in these newborn infants.

STUDY DESIGN

Three groups were defined in this prospective study: group 1, healthy neonates with no risk factors (n = 40); group 2, neonates who had severe hypoxia (n = 20); and group 3, neonates who fulfilled the criteria for early-onset sepsis (n = 18). Blood samples were collected for complete blood cell count and serum M-CSF levels by peripheral venipuncture from each infant in the first 24 hours after birth before any medical therapy.

RESULTS

The gestational ages and birth weights did not differ significantly between the groups. Serum M-CSF levels of the septic neonates were significantly higher than of both healthy and hypoxic neonates, but did not differ significantly between the healthy and hypoxic neonates. There was no significant correlation between serum M-CSF levels and circulating monocyte counts, but there was a significant inverse correlation between serum M-CSF levels and thrombocyte counts. When this correlation was analyzed according to groups, we determined that this inverse correlation between M-CSF levels and thrombocyte counts was especially significant in the septic neonate group, but not significant in the healthy and hypoxic neonate groups.

CONCLUSIONS

Serum M-CSF levels are significantly higher in neonates with sepsis. High serum M-CSF levels may have a possible role in the pathogenesis of thrombocytopenia in neonates with sepsis.

[Neonatal hemorrhagic syndromes]

PURPOSE

The purpose of our study was to clarify the frequency of these causes.

PATIENTS AND METHODS

Retrospective study using reports of newborns in the neonatal unit in Sousse (Tunisia) from 1991 to 1996, hospitalized for hemorrhagic syndrome defined by bleeding, exteriorized or not, whatever its importance, severity, causes and the associated clinical and biological disorders. Isolated meningeal hemorrhages, limited cutaneo-mucous hemorrhages (conjunctival hemorrhages, bruises), and genital crises of the newborn, were excluded.

RESULTS

One hundred and fifty-five hemorrhagic syndromes were observed from 7,128 newborn infants (2.17% of hospitalization). Sex ratio was 1.42. Prematurity rate was 35.7%. The Apgar score was < 7 at one minute in 40.7% of cases. Disorders associated with hemorrhagic syndromes were observed in 118 newborn infants (76.1%) with a predominance of neonatal infections (35.6%). The etiology of neonatal hemorrhages was specified in 93% of cases: newborn hemorrhagic disease (27.7%), disseminated intravascular coagulation (27.1%), isolated thrombocytopenia (9%), digestive lesions (13.5%), and obstetrical trauma (2.6%).

CONCLUSION

The frequency of the newborns hemorrhagic syndromes underlines the need for its systematic prevention by vitamin K in the antenatal period to the mother and after birth to the newborn.

Neonatal alloimmune thrombocytopenia due to anti-Nak(a)

BACKGROUND

The accurate diagnosis of neonatal alloimmune thrombocytopenia is essential in the effective treatment of potentially serious bleeding in neonates.

CASE REPORT

Reported here is a case of a full-term female baby who was delivered by vacuum extraction from a gravida 1 para 1 healthy mother. She presented with generalized petechiae and bilateral cephalhematoma, which she had had since birth. At 7 hours of life, she had an upper gastrointestinal hemorrhage and was found to have severe anemia and marked thrombo-cytopenia. Coagulation screening tests were normal. The diagnosis of neonatal alloimmune thrombocytopenia was suspected, and maternal serum was collected for further study. The baby was treated with a single dose of hydrocortisone (10 mg/kg) and IVIG (400 mg/kg) while waiting for irradiated platelets from her mother. After 30 mL of a transfusion of maternal platelets, the baby's platelet count rose dramatically, from 15,000 to 162,000 per microL, and it remained stable at that level. She was discharged on the 10th hospital day in good condition. During the follow-up period of 8 months, her growth and development were satisfactorily normal, as well as her platelet count. A high-titered platelet antibody was detected in the maternal serum by use of a solid phase platelet adherence technique.

RESULTS

The specificity of the platelet antibody was identified as anti-Nak(a) by the mixed passive hemagglutination test method.

CONCLUSION

These findings suggested a diagnosis of NAIT caused by anti-Nak(a).

Neonatal thrombocytopenia: new insights into pathogenesis and implications for clinical management

The healthy fetus has a platelet count of greater than 150 x 10(9)/L by the second trimester of pregnancy and only 2% of term infants are thrombocytopenic at birth. Severe thrombocytopenia (platelets < 50 x 10(9)/L) occurs in fewer than three per 1000 term infants, the most important cause being alloimmune thrombocytopenia. In contrast, in infants admitted to neonatal intensive care units, thrombocytopenia develops in 25% and in up to half of sick preterm infants. Recent evidence shows that these infants mostly have evidence of underlying impaired fetal megakaryocytopoiesis and platelet production following pregnancy complications characterized by placental insufficiency or fetal hypoxia. The mechanism of this is unknown. However, many neonatal complications exacerbate this thrombocytopenic potential and 20% of thrombocytopenias in neonatal intensive care unit patients are severe. Evidence-based guidelines for platelet transfusion therapy in these patients are yet to be defined, but as platelet underproduction underlies most neonatal thrombocytopenias, recombinant hemopoietic growth factors, including thrombopoietin and interkeukin-11, may be useful future therapies.

Evaluation and treatment of thrombocytopenia in the neonatal intensive care unit

Thrombocytopenia is a very frequent problem among sick neonates, affecting up to 35% of all infants admitted to the NICU. Although multiple clinical conditions have been causally associated with neonatal thrombocytopenia, the cause of the thrombocytopenia is unclear in up to 60% of affected neonates. This article provides neonatologists with a practical approach to the thrombocytopenic neonate, with an emphasis on conditions that could be life-threatening or could have significant implications for further pregnancies. An overview of the current therapeutic modalities is also presented, including a discussion of the possible use of recombinant thrombopoietic cytokines to treat certain groups of thrombocytopenic neonates.

Thrombopoietin in the fetus and neonate

C-mpl ligand or thrombopoietin (Tpo) is increasingly recognised as the major regulator of platelet homeostasis in humans. Relatively little is known about Tpo in the fetus and neonate but no evidence has yet been found to suggest any fundamental difference in Tpo structure, function and regulation in the fetus and neonate compared to older age groups. Tpo mRNA transcripts have been detected in the fetus as early as 6 weeks post conception and the liver appears to be the main site of Tpo production in both the fetus and neonate. The vast majority of healthy newborns have detectable levels of circulating Tpo and raised Tpo levels are commonly, but not consistently, found in thrombocytopenic neonates. In adults receptor binding and subsequent metabolism of Tpo is proposed as the main method of regulation of the circulating Tpo level. Preliminary studies in neonates showing increased Tpo levels most often during thrombocytopenia accompanied by reduced megakaryocytopoiesis supports this concept. In addition to this demonstrable fetal and neonatal endogenous Tpo production megakaryocyte progenitor and precursor cells from the fetus and from preterm and term newborns proliferate and differentiate extensively in-vitro in response to exogenous Tpo. Furthermore a recent study has shown a marked rise in platelet count in newborn rhesus monkeys administered one form of recombinant Tpo. Although these studies remain at an early stage together these findings strongly suggest that, as in adults, Tpo is the major regulator of platelet homeostasis in the fetus and neonate. Thrombocytopenia is common in sick neonates and progress in understanding this important clinical problem is likely to be greatly enhanced by the current and future research into Tpo production, function and regulation in the healthy and thrombocytopenic fetus and neonate.

[Perinatal thrombocytopenia of maternal origin]

Maternal causes of perinatal thrombocytopenia include neonatal alloimmune thrombocytopenia, autoimmune disorders, intrauterine infections and hypertensive diseases. The diagnosis of these pathologies is difficult because they can occur in sick neonates, but also in healthy babies without a history suggesting illness. The treatment has to be quickly established in order to decrease eventual hemorrhagic complications. These latter can be amplified by several clinical circumstances and especially by the platelet immaturity of this time of life. The risk of recurrence for the next pregnancies has to be determined and can lead to diagnostic or therapeutic measures during the antenatal period.

Approach to the bleeding newborn

Bleeding in the newborn can lead to serious cardiovascular and neurological effects. Routine administration of vitamin K has reduced the incidence of hemorrhagic disease of the newborn, but abnormal bleeding can occur in babies from many causes. A practical approach to the diagnosis and treatment of bleeding in the newborn is described in this article.

Purpura in infants and children

Hemorrhage into the skin (purpura) may result from abnormalities in any of the three components of hemostasis: platelets, plasma coagulation factors, and blood vessels. The morphology, size, and distribution of the hemorrhagic lesions are helpful diagnostic features. The main causes of purpura in the newborn and the more common hemorrhagic disorders in children are reviewed.