A 6-day-old girl who was born at home is being evaluated for bruising and gastrointestinal bleeding

A 6-day-old girl who was born at home is being evaluated for bruising and gastrointestinal bleeding. Laboratory findings include partial thromboplastin time and prothrombin time, greater than 2 minutes; serum bilirubin, 4.7 mg/dL; alanine aminotransferase, 18 mg/dL; platelet count, 330,000/mm3; and hemoglobin, 16.3 g/dL. Which of the following is the most likely cause of her bleeding?

A. Factor VIII deficiency
B. Factor IX deficiency
C. Idiopathic thrombocytopenic purpura
D. Liver disease
E. Vitamin K deficiency

Explanation: The correct answer is E. The infant in this clinical vignette has hemorrhagic disease of the newborn as a result of vitamin K deficiency. It was a major cause of bleeding in neonates in the past, but it is now uncommon because of the routine administration of vitamin K at birth. However, it is still encountered in situations in which babies are born outside the hospital. The normal newborn has a moderate deficiency of the vitamin K–dependent coagulation factors. The plasma levels of these factors fall even further during the first 2-5 days of life, rise again when the infant is 7-14 days old, and attain normal adult levels at about 3 months of age. This variation usually does not produce any bleeding or bruises. However, in hemorrhagic disease of the newborn, the initial fall is accentuated, and the restoration is delayed and incomplete. As a result, coagulation abnormalities become severe and bleeding may occur. All newborns should receive 0.5-1.0 mg of vitamin K intramuscularly within the first hour after birth.

Prematurity has been associated with hemorrhagic disease of the newborn. Delayed feeding, breast-feeding, vomiting, severe diarrhea, and antibiotics also delay the colonization of the gut by bacteria.

Bleeding is usually severe and occurs most commonly on the 2nd or 3rd day of life. The most common manifestations are melena, large cephalohematomas, and bleeding from the umbilical stump and after circumcision. Generalized ecchymoses, often without petechiae, intracranial bleeding, and large intramuscular hemorrhages, also may develop in severe cases. In infants with hemorrhagic disease of the newborn, the prothrombin time (PT) is always prolonged. The partial thromboplastin time (PTT) and the thrombin time are also prolonged. Specific factor assays reveal deficiencies of prothrombin; factors VII, IX, and X; and proteins C and S. The bleeding time and the platelet count usually are within normal limits. In the differential diagnosis of hemorrhagic disease of the newborn, virtually all causes of bleeding, particularly thrombocytopenia and disseminated intravascular coagulation (DIC), must be considered.

Factor VIII deficiency (choice A), or hemophilia A, is caused by factor VIII deficiency. Factor VIII is the critical cofactor for generation of factor Xa by factor IXa. Significant prolongation of the PT is not found in hemophilia A.

Factor IX deficiency (choice B), or hemophilia B, is not associated with significant prolongation of the PT.

Idiopathic thrombocytopenic purpura (choice C) is usually characterized by a platelet count of <20,000/mm3. It often follows an acute infection and has spontaneous resolution within 2 months.

Liver disease (choice D) would cause prolongation of PT and PTT, as well as liver enzymes.