Neonatal factor XIII deficiency.
We describe a patient diagnosed in the neonatal period as having factor XIII deficiency who presented with persistent umbilical bleeding. Factor XIII deficiency is the only coagulation factor deficiency that cannot be detected by classical hemostatic tests, and a rapid diagnosis is vital during the first decade of life. A newborn presenting with persistent umbilical stump bleeding should be screened for factor XIII deficiency when routine coagulation tests prove normal.