[Foetal/neonatal alloimmune thrombocytopenia. A review and case report].

Foetal/neonatal alloimmune thrombocytopenia is the most common cause of severe thrombocytopenia in the newborn. It is an acute disorder which implies that foetal platelets are destroyed during the pregnancy due to a maternal alloimmune IgG antibody. More than 80% of Caucasians are HPA-1a specific. Intracranial haemorrhage, which occurs in 30% of cases, is the most serious complication, with a 10% mortality rate or a 20% rate of irreversible neurological sequels. The high risk of a recurrence of serious bleeding in future pregnancies led us to consider prophylaxis or prenatal treatment. An early diagnosis of this process allows an effective therapy to be carried out based on the infusion of compatible phenotype HPA platelets or endovenous immunoglobulins. We present the case of a 27 year old pregnant woman, who in the 35th week of a second pregnancy was diagnosed using echography with a bilateral foetal hydrocephaly. After caesarean delivery in the 36th week, the newborn presented haematomas in the left shoulder and gluteus, macrocephalia with tension of the fontanellas and hemorrhagic cerebrospinal fluid after insertion of an external ventricular derivation catheter. The haemogram revealed a severe trombocytopenia (9 x 109/L). In the light of clinical suspicion of foetal/neonatal alloimmune thrombocytopenia, infusion was made of platelets from a non-phenotyped donor for the HPA-1a system, and an endovenous immunoglobulin treatment was followed, with a recovery of platelet counts, but with neurological sequels that are probably irreversible. The immunohaematologal study confirmed the negative HPA-1a maternal phenotype, the neonatal HPA-1a positive phenotype and the presence of anti-HPA-1a alloantibodies in the maternal serum. Nowadays, the prophylaxis and treatment continue to be a controversial issue that is open to discussion, as is the possibility of implementing antenatal screening.