Anti-HPA-3A induces severe neonatal alloimmune thrombocytopenia.
OBJECTIVE
Fetal and neonatal alloimmune thrombocytopenia (AIT) caused by feto-maternal incompatibility at the HPA-1a (PLA-1) locus is well characterized. Alloimmunization and disease caused by HPA-3a is rare.


METHODS
We conducted a retrospective analysis of all known cases of AIT caused by HPA-3a incompatibility identified at 3 major reference laboratories from 1986 to 1996. Platelet antigen typing and antibody specificity were determined by serologic evaluation. In some cases confirmatory genotyping was performed.


RESULTS
Fourteen cases of anti-HPA-3a-induced AIT in 11 families were identified. Five patients had a previous affected sibling, and 2 cases were firstborn children. All patients had severe thrombocytopenia at birth (platelet count <20 x 10(9)/L). Regardless of therapy, the median time to platelet recovery was 6 days (range, 3 to 23 days). Two (15%) patients had documented intracranial hemorrhage, 1 with severe sequelae including apnea and convulsions. A literature review describing 16 additional patients corroborates the finding of severe thrombocytopenia and a significant incidence of intracranial hemorrhage caused by HPA-3a incompatibility.


CONCLUSIONS
AIT caused by incompatibility of HPA-3a is similar in severity to disease caused by incompatibility of HPA-1a. Affected families should be appropriately counseled and considered for antenatal therapy.
Glade-Bender
J
J
Department of Pediatrics, Division of Hematology/Oncology, New York Presbyterian Hospital, 525 E 68th St., P695, New York, NY 10021, USA.
McFarland
J G
JG
Kaplan
C
C
Porcelijn
L
L
Bussel
J B
JB
D016824:Antigens, Human Platelet / Q000276:immunology*; D002543:Cerebral Hemorrhage / Q000209:etiology; D006801:Humans; D007231:Infant, Newborn; D010976:Platelet Count; D017713:Platelet Transfusion; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000276:immunology* / Q000628:therapy; D012189:Retrospective Studies
C044561:3a alloantigen, human; D016824:Antigens, Human Platelet