Prenatal diagnosis of platelet disorders

The antenatal diagnosis of platelet disorders represents real progress in the early detection of haemorrhagic diseases occurring in the fetus. However, the diagnosis is only possible in some cases during the first trimester of gestation, and not in the first weeks as is the case for other hereditary disorders such as abnormal haemoglobins. This delay can be reduced now that the molecular abnormalities responsible for some platelet disorders have been discovered. If the region of chromosome 17 and the DNA sequence coding for the glycoproteins GP IIb-IIIa were known, this would make possible the recognition of the gene defect responsible for Glanzmann's thrombasthenia. This could also permit the diagnosis of Glanzmann's thrombasthenia at the gene level, i.e. during the first weeks of gestation. However, the use of gene markers could be limited by the fact that a monomorphic clinical expression of Glanzmann's thrombasthenia could correspond to different genetic mutations which can all result in a defect in GP IIb-IIIa synthesis and assembly. If such diagnosis could be made very early, it would only represent real progress if a specific treatment could be applied. New therapeutic approaches to immune thrombocytopenia during pregnancy appear to be possible and can be applied when there is a risk to the fetus, they are still either experimental or anecdotal and there is a real need for a well-designed clinical trial. In all fetal platelet disorders, the risk of fetal death following fetal blood sampling must not be underestimated and very careful, intensive care is necessary after such an investigation. In the absence of a specific therapy, this antenatal diagnosis must be restricted to cases in which the risk of severe haemorrhagic complications are anticipated and where there is a well-documented family history. The patients must be properly informed of all the aspects of the investigation, including the possible risks. As has been the case for other haematological disorders, progress will be made, and we can anticipate that eventually in utero bone-marrow transplantation or gene correction be performed to cure the disease before birth.