Inherited resistance to activated protein C in a boy with multiple thromboses in early infancy.

Resistance to activated protein C is a recently discovered genetic defect with a high prevalence in adult patients with thromboembolic disease. It is an autosomal dominant disorder and is ten times more common in these patients than antithrombin III-, protein C- and protein S deficiency together. In spite of this high prevalence among adults with thromboembolic disease no clinical manifestation in infancy so far has been reported. We describe a 4-year-old boy with a complex cardiac malformation and inherited resistance to activated protein C, who developed multiple thromboses after cardiac catheterization in early infancy. Conclusion. Resistance to activated protein C can cause thrombosis in infants and children if additional risk factors for the development of thrombosis are present.