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Thrombocytopenia

Summary

  • the well infant who presents unexpectedly on the first day of life with extensive bruising and/or a petechial rash and who is found to have isolated thrombocytopenia (TP) (platelet count <100 x 109/L) without an obvious cause must be presumed to have neonatal alloimmune thrombocytopenia until proven otherwise
  • although mild TP is common, most infants do not require treatment
  • the decision to provide a platelet transfusion should depend on the presence or absence of symptoms, sepsis, DIC, surgery or invasive procedures

Introduction

Thrombocytopenia (TP) in the newborn is defined as a platelet count less than 150 x 109/L. This occurs in 1-4% of all newborn babies. The majority of episodes of TP present during the first 72 hours of life.

The highest incidence of TP is in sick, preterm babies (40-70%). Indeed, TP is the most common haematological abnormality in the NICU. Nearly 25% of sick infants develop TP, which is trivial for some infants with a platelet count of 100-150 x 109/L. In more than 50% of affected infants platelet counts fall below 100 x 109/L and 20% of infants have platelet counts <50 x 109/L.

Automated platelet counts may be abnormally low due to platelet aggregation in sample. Low results should be confirmed by blood film examination and often a repeat sample (arterial or venous).

This topic focuses on the differential diagnosis and management of TP. Because the most likely cause of severe TP in a baby remaining in a level ll hospital is Neonatal Alloimmune TP (NAIT), special attention is given to this condition. NAIT is often referred to as Fetomaternal alloimmune thrombocytopenia (FMAIT)

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Differential Diagnosis of thrombocytopenia in babies by age at presentation

  • Fetus
    • neonatal alloimmune TP (NAITP)
    • maternal autoimmune disease (Idiopathic TP, SLE)
    • congenital infections (CMV, Toxoplasmosis, Rubella)
    • severe rhesus disease
    • chromosomal disorders (trisomy 21, 18, 13)
    • rare inherited disorders (TAR - TP with Absent Radii)

  • Neonate < 72 hours of age
    • placental insufficiency (PET, IUGR, diabetes)
    • birth asphyxia
    • perinatal bacterial infection (GBS, E. coli. Listeria)
    • congenital infection (CMV, Toxoplasmosis, Rubella)
    • NAITP
    • maternal autoimmune disease (ITP, SLE)
    • thrombosis (renal vein, aortic)
    • rare inherited disorders (TAR, Wiskott-Aldrich syndrome)

  • Neonate > 72 hours of age
    • bacterial infection (nosocomial)
    • infected indwelling lines
    • NEC
    • maternal autoimmune disorders (ITP, SLE)
    • congenital infection (CMV, Toxoplasmosis, Rubella)
    • rare inherited disorders (TAR, Wiskott-Aldrich syndrome)

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Neonatal Alloimmune Thrombocytopenia (NAITP)

  • in contrast to Rh alloimmunisation, 40-60% cases in first born
  • 75-90 % subsequent pregnancies are affected
  • severe cases in fetus or newborn occur in 1 in 1200 pregnancies
  • untreated, intracranial haemorrhage occurs in 10-30% of cases
  • overall fetal and neonatal mortality in 6-13% of cases
  • long-term neurodevelopmental sequelae in 20-25% of survivors
  • diagnosed by demonstration of fetomaternal incompatibility for a platelet surface antigen and presence of maternal platelet alloantibodies that react with a 'foreign' antigen present on platelets of the infant and father but not the mother's platelets
  • all children with suspected or proven NAITP warrant a cranial ultrasound to exclude intracranial haemorrhage

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Platelet function (but not absolute count) may be impaired with

  • maternal aspirin - not usually severe
  • Indomethacin
  • infant of diabetic mothers - possibility of enhanced platelet reactivity
  • rarely inherited platelet function defect

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Management of Thrombocytopenia

Note that the risk of bleeding is increased where there is

  • decreased production rather than increased destruction
  • platelet function defect plus thrombocytopenia
  • the platelet count < 50 x 109/L

There is no accepted 'safe' level of platelets in neonates. Platelet transfusions need to be considered for each individual based on the platelet count, the clinical circumstance and the presence or absence of bleeding. The underlying cause should be treated, if possible.

Potential triggers for platelet transfusion include

 Platelet Count

 Clinical Condition
Normal platelet count Platelet dysfunction and clinical bleeding
Platelet count < 100 Major bleeding
Surgery
DIC and bleeding
Sepsis with rapid deterioration
Platelet count < 50 Minor bleeding
Exchange transfusion
Preterm
Platelet count < 30 Asymptomatic term infant


The recommended volume of platelets to be transfused is 10 - 20ml/kg. This should transiently increase the platelet count by 50 - 100 x 109/L. Transfuse over 30 minutes and monitor platelet count 1 hour post transfusion. Ensure that the platelets are

  • leukocyte-depleted
  • CMV-negative (if unknown, filtering may be required before transfusion)
  • where possible, ABO compatible plasma
  • irradiated if infant is immunocompromised

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Specific treatment required for NAITP

  •  use washed, irradiated maternal platelets (certain compatibility, availability, safety)

OR

  • antigen-compatible donor platelets

 

  • random platelets only in emergency situations are often the only available therapy in the initial instance as delays to platelet transfusion should be avoided, platelet increment can be improved by giving IVIg 1g/kg immediately prior to platelet transfusion
  • high dose intravenous IgG may be effective in the absence of/in addition to maternal platelets
    • 1 g/kg for 2 days

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Areas of uncertainty in Clinical Practice

  • a 'safe' platelet count for newborn infants has not yet been identified
  • evidence-based guidelines for platelet transfusion therapy are yet to be defined
  • there is little evidence that steroids and exchange transfusion have a therapeutic role in NAITP

References

Chakravorty S, Murray N, Roberts I. Neonatal Thrombocytopenia Early Human Development 2005; 81:35-41

 

Roberts IAG, Murray NA. Review. Management of thrombocytopenia in neonates. Br J Haematol 1999; 105:864-70

Blanchette VC, Johnson J, Rand M. The management of alloimmune neonatal thrombocytopenia. Bailliere's Clinical Haematology 2000;13:365-90

Letsky EA, Greaves M. Guideline. Guidelines on the investigation and management of thrombocytopenia in pregnancy and neonatal alloimmune thrombocytopenia. Br J Haematol 1996;95:21-26

Roberts AG, Murray NA. Neonatal thrombocytopenia: new insights into pathogenesis and implications for clinical management.
Current Opinion in Pediatrics. 2001;13:16-21

Rayment R, Brunskill SJ, Stanworth S, Soothill PW, Roberts DJ, Murphy MF. Antenatal interventions for fetomaternal alloimmune thrombocytopenia. Cochrane Database of Systematic Reviews 2005, Issue 1. Art. No.: CD004226. DOI: 10.1002/14651858.CD004226.pub2


Bassler D, Greinacher A, Okascharoen C, Klenner A, Ditomasso J, Kiefel V, Chan A, Paes B.A systematic review and survey of the management of unexpected neonatal alloimmune thrombocytopenia.Transfusion. 2008 Jan;48(1):92-8. Epub 2007 Sep 24

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