A breastfed term infant born at home presents on day 4 of life with oozing from the umbilical stump and cephalhematoma. PT and aPTT are both prolonged. The underlying defect is:

• A Deficiency of fibrinogen due to immature hepatocytes
• B Impaired gamma-carboxylation of factors II, VII, IX and X ✓
• C Consumption of platelets in disseminated intravascular coagulation
• D Congenital absence of von Willebrand factor

Explanation

Vitamin K deficiency bleeding of the newborn occurs at 2 to 7 days in unsupplemented infants, especially exclusively breastfed ones, because breast milk contains very little vitamin K and the sterile newborn gut synthesizes none. Vitamin K is the cofactor for gamma-carboxylation of glutamate residues on factors II, VII, IX and X, so both PT and aPTT prolong. Platelet count and fibrinogen are normal, excluding DIC, and vWD does not prolong aPTT typically.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.