Definition
§ Platelet count <150,000 in a neonate
Background
§ Fetuses begin making platelets 5 days post conception and reach adult levels by 22w gestation
o For this reason, the definition of thrombocytopenia has the same parameters as adults
o Platelet counts increase with increasing postnatal age
o Recent studies questioning the validity of using adult parameters for neonates, but no change in definition yet
§ Normal term neonates have incidence of thrombocytopenia <1% while the incidence for NICU admits is 18-35%
§ Most cases are mild and resolve within 7-14 days, but a small subset of cases (2.5-5%) are severe and take months to resolve
§ Severe, persistent, and symptomatic patients must be evaluated
Etiology
§ Increased Platelet Destruction
o Alloimmune thrombocytopenia: maternal ab against fetal platelets
§ Neonatal Alloimmune Thrombocytopenic Purpura (NATP): fetal platelets contain an antigen inherited from the father that the mother lacks. Mother makes IgG against the paternal antigen which crosses the placenta and causes thrombocytopenia
· Infants are at risk for intracranial hemorrhage. 25-50% occur in utero
o Autoimmune thrombocytopenia: maternal ab against maternal and fetal platelets
§ SLE, ITP: maternal ab against maternal and fetal platelets
§ Drug-related: maternal or fetal ab
· antiepileptics, quinidine, PCN, heparin, hydralazine, thiazides
o Peripheral Consumption
§ Hypersplenism
§ Kasabach-Merritt Syndrome: DIC with capillary hemangiomas
§ DIC
§ Infection: bacterial, viral, or fungal.
§ Necrotizing enterocolitis
§ Thrombosis
§ Hemorrhage (most IVH, pulm, or GI)
· premature IVH: normal platelet counts at time of bleed, so causal relationship difficult to determine
· term IVH: thrombocytopenia common at time of bleed
§ Decreased Platelet Production
o Genetic Disorders
§ Thrombocytopenia-absent radius syndrome: AR, bilateral absent radii, thumbs present
§ Fanconi’s Anemia
§ Congenital amagakaryocytic thrombocytopenia
§ Chromosome abnormalities: trisomies (21, 18, 13), Turner syndrome
§ Congenital platelet disorders: Wiskott-Aldrich, May-Hegglin, Bernard-Soulier, Alport
o Infiltrative Disorders: neoplasms. Rare in the neonatal period.
o Toxic injury to megakaryocytes by infections/drugs
§ Miscellaneous Causes
o Neonatal Cold injury: mechanism unclear
o Asphyxia: mechanism unclear, but possibly related to hypoxic injury
o Von Willebrand Disease: platelet aggregation
o Preeclampsia: nadir at 2-4 days with resolution typically by 7-10 days
o Dilution
Management
§ Initial evaluation
o Thorough history and physical exam of mother and neonate, including birth history
§ Healthy appearing infant more likely to have congenital/immunologic mediated cause
§ Ill appearing infant more likely to have infection, DIC, NEC, asphyxia as cause
o Labs:
§ Neonate: CBC (repeated to confirm thrombocytopenia), platelet ag typing, peripheral smear, coags, sepsis work up if ill appearing, eval for congenital infection, genetic testing
§ Maternal: CBC (repeated to confirm thrombocytopenia if present), platelet ag typing
o Cranial US to evaluate for IVH. If present, low threshold for transfusion. Repeat prior to discharge
§ Treatment
o If underlying cause known (mom with SLE, ITP, known infection, etc), treat.
o Platelet counts should be more aggressively maintained for first 72-96 hours of life as risk for IVH highest in this time period. If no IVH, then clinical situation used to guide need for transfusion
§ High dose IVIG for 3-4 days is used as adjunct
§ Methylprednisolone used only in emergency situations as evidence lacking
o When to transfuse?
§ No clear guidelines
§ Term infant, healthy, no other risks for hemorrhage: typically if <30,000
§ Preterm, ill, or with other risk factors: typically if <50,000
§ Benefit of platelet transfusion not clearly established; some recent suggestion that transfusion may be harmful
o Other therapies
§ IVIG, steroids, exchange transfusion typically used for immune mediated causes
§ Current research into using thrombopoeitic mimetics as an alternative to transfusion
References
Murphy S. Consultation with the Specialist. Thrombocytopenia. Pediatrics in Review. Feb 1999; 20(2): 64-68.
Albert TS. Throbopoietin in the Thrombocytopenic Term and Preterm Newborn. Pediatrics. June 2000; 105(6):
1286-1291.
Silver RM. Neonatal Alloimmune Thrombocytopenia: Antenatal Management. American Journal of Obstetrics and
Gynecology. May 2000; 182(5): 1233-1238.
Behrman: Nelson Textbook of Pediatrics, 16th ed (2002). Philadelphia: W.B. Saunders Company.
Gomella: Neonatology:
Management, Procedures, On-Call Problems, Diseases
and Drugs, 4th ed (1999). McGraw
-Hill/Appleton
and Lange.
Ferrar-Marin
F, et al. Neonatal Thrombocytopenia and Magakaryocytopoeisis. Seminar
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Hematology. July
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47 (3) 281-288
UpToDate. Neonatal Thrombocytopenia.