These mechanisms are not mutually exclusive, and some infants (particularly sick or premature infants) present with a combination of these mechanisms.
Alloimmunization to inherited paternal platelet antigens and destruction of fetal platelet can occur during the first pregnancy with an antigen incompatible fetus thus presenting a severe thrombocytopenia in an otherwise healthy neonate.
The mom produces antibodies that attack the baby's platelets causing thrombocytopenia. The baby has one platelet antigen from the mom, which the mom recognizes as &quot;self&quot; and one from the father that is of the opposite type, which triggers the immune response.
The Ab is directed against antigens common to maternal and neonatal platelets.
the platelet count should be repeated daily for the next three to four days, as platelet counts are commonly at their lowest during this time before rising spontaneously by day 7 in most cases. As most babies found to have an ICH secondary to maternal autoimmune disorders have had platelet counts of < 30 ´ 109/l.
NEONATALTHROMBOCYTOPENIA By: Adrian B. Jayawon Ma. Joselle L. Balasa Katrina Kaye C. Bañas Nikki Marie O. Blanco Karleen T. Buenasflores
Thrombocytopenia• Defined as a reduction of platelet in the peripheral blood count of < 150, 000µL.• Reconfirmation of the platelet count should be done.• Confirmation by Blood Film
Pathophysiology• Decreased platelet production (usually in sick or premature infants)• Increased platelet destruction (immune or consumptive)• Platelet pulling to splenomegaly (rare)
Decreased Production• Thrombocytopenia in sick neonates is low to the secondary to decreased megakaryopoiesis as a result of neonatal asphyxia or infection.• In very sick neonates with disseminated intravascular coagulopathy (DIC), there may be platelet destruction• Bacterial or viral sepsis with or without disseminated intravascular coaguopathy.
Increased Platelet Destruction• Infants with immune-mediate thrombocytopenia have increased platelet destruction, usually without decreased production.• Compensatory increase in megakaryopoiesis is often observed in the bone marrow.• Thrombocytopenia occurs in about 10% of infants whose mothers have ITP.
• Infants with Kasabach-Merrit Syndrome (KMS) usually have severe thrombocytopenia, and often have evidence of DIC.• Thrombocytopenia and coagulopathy is presumed to be due to platelet trapping on the endothelium of the Kaposiform Hemagioendothelioma (KHE), but can also be a result of DIC.
• May also occur secondary to thrombosis of a major vessel.• Result from platelet consumption at the site of thrombosis.
Neonatal Alloimmune Thrombocytopenia• Most frequent cause of thrombocytopenia in the first few days of life of a healthy infants.• Severe and can cause serious bleeding; such as intracranial hemorrhage (ICH)
Etiology• Antibodies to the HPA-1a is responsible for more than 75% of NAIT cases, while antibodies to the HPA-5b and other platelet antigens being implicated in a minority cases.
• The risk of HPA-1a alloimmunization is highest in women who are HLA class II DRB3*0101
Pathophysiology• Maternal IgG alloantibodies formed in the maternal circulation and cross the placenta that leads to the destruction of fetal platelets.• The mother has a normal platelet count, while the fetus can be severely thrombocytopenic.
Clinical Manifestation• Occur as early as 20 weeks gestation, often severe (platelet count <20, 000/ µL)• Major bleeding, particularly intracranial hemorrhage (ICH), occurs in 10-20% of untreated NAIT cases.• Affected infants may present asymptomatic severe thrombocytopenia, or with mild bleeding symptoms such as petechiae or purpura
Diagnosis and Treatment• Diagnosed when platelet antigen incompatibility is found between the parents, maternal serum of antibody reacts with platelets from the infant and father not with platelets from the mother• Peripheral smear for the abnormalities and confirmation of thrombocytopenia is important
Autoimmune Neonatal ThrombocytopeniaEtiology: Neonatal autoimmune thrombocytopenia canoccur in infants born to women with ITP. Maternal IgGautoantibodies cross the placenta and bind to neonatal(and fetal) platelets, and cause platelet destruction bymacrophages in the reticuloendothelial system.
Pathophysiology There was a concomitant drop in the level ofmaternal antiplatelet antibody on the child’s platelets.
Clinical Manifestation • less severe than in NAITP • risk of ICH is 1% or less
Diagnosis and Treatment• Blood Test• CBC• Platelet antibody tests• All neonates of mothers with autoimmune disease should have a cord blood platelet count determined at birth and again at 24 hours.• IVIG regardless of whether or not there is evidence of bleeding