BRa (HPA-5b) incompatibility may cause thrombocytopenia in neonates of mothers with immune thrombocytopenic purpura.
OBJECTIVE
The association of anti-Br(a) immunoglobulin G (IgG) platelet alloantibodies with the development of thrombocytopenia in neonates of mothers with autoimmune thrombocytopenic purpura (ITP) is reported.


METHODS
Between March 1994 and July 1997, 28 consecutive pregnant women with ITP seen at New York Hospital were screened for platelet-reactive antiglycoprotein (glycoprotein [GP] IIb/IIIa, Ib/IX, and Ia/IIa) antibodies.


RESULTS
The sera from 6 of these 28 women contained IgG alloantibodies to GP Ia/IIa directed against the Br(a) (HPA-5b) antigen. Only three families each had at least one Br(a)+ and at least one Br(a)- infant. Platelet typing in these families revealed that the mothers were Br(b/b) (Br(a)-) and the fathers were Br(a/b) (Br(a)+). Platelet counts < 100,000/microl occurred only in 2 of the 3 infants who were Br(a)+. The platelet counts were significantly lower in the three Bra+ infants compared to the five Br(a)- infants (p = 0.038).


CONCLUSIONS
Platelet alloimmunization with anti-Br(a) can cause neonatal thrombocytopenia in infants of mothers with ITP. Platelet antibody testing in the pregnant women with ITP is recommended.
Gururangan
S
S
Department of Pediatrics, New York Hospital-Cornell University Medical Center, New York 10021, USA.
McFarland
J G
JG
Cines
D B
DB
Skupski
D
D
Bussel
J B
JB
D016824:Antigens, Human Platelet / Q000276:immunology*; D000939:Epitopes / Q000276:immunology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000276:immunology*; D007518:Isoantibodies; D010641:Phenotype; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology; D011247:Pregnancy; D011446:Prospective Studies; D011696:Purpura, Thrombocytopenic / Q000276:immunology*; D013921:Thrombocytopenia / Q000276:immunology*
C055973:5b alloantigen, human; D016824:Antigens, Human Platelet; D000939:Epitopes; D007518:Isoantibodies; D019039:Platelet Glycoprotein GPIIb-IIIa Complex