[Neonatal alloimmune thrombocytopenia following immunization against the platelet antigen ZWA (PLA/1). 3 case reports in the same family and analysis of the literature]. / Les thrombopénies néonatales allo-immunes par immunisation contre l'antigène plaquettaire ZWA (PLA/1). A propos de trois cas d'une même famille et analyse de la littérature.

Allo-immune neonatal thrombopenia is to platelets what rhesus hemolytic disease is to red blood cells. There is a risk of haemorrhage when fetal platelets decreases below 50,000 per mm3. Such haemorrhage may occur at any time during the thrombopenia period. However they are mostly due to obstetrical traumatisms during delivery. Lethal complications and severe neurologic sequellae is estimated to affect about 30% of newborns: 1/3 these complications occur in utero and 2/3 during delivery. The authors have studied 3 familial cases of foeto-maternal allo-immunisation occurring with the PLA 1 system. They have made a briefing of the physiological, the pathological and the epidemiological aspects of such immunisation before insisting upon case findings of such affected fetus. A capillary blood sample taken from the scalp of the fetus at the beginning of labour allows a safe natural delivery if fetal blood count shows more than 50,000 platelets per mm3. A fetal blood sampling under ultrasonographic guidance will bring about to an early diagnosis and prognosis, this allowing an adequate treatment for fetus with a high risk of thrombopenia.