Prenatal Diagnosis of Hereditary Protein C Deficiency

To the Editor: Protein C is a naturally occurring vitamin K—dependent zymogen, which in its activated form is a potent anticoagulant directed against factors V and VIII.¹ Heterozygous protein C deficiency is manifested by recurrent venous thromboembolism at a relatively young age, which is manageable by oral anticoagulant treatment.^2,3 The homozygous state presents in the neonatal period as overwhelming venous thrombosis⁴ or purpura fulminans,^{5 6 7 8} with a high mortality rate. We have successfully carried out second-trimester prenatal diagnosis in a fetus at risk of homozygous protein C deficiency by fetal-blood sampling. The mother was a 34-year-old woman who had lost two.