A neonate develops hemorrhage on day 3 of life. PT and aPTT are both prolonged, platelet count is normal, fibrinogen is normal, and there is no family history. Mixing studies correct both PT and aPTT. The diagnosis is:
- A Hemorrhagic disease of newborn (Vitamin K deficiency bleeding) — deficiency of factors II, VII, IX, X ✓
- B Hemophilia A (factor VIII deficiency) — X-linked, prolongs aPTT only
- C Disseminated intravascular coagulation — all clotting factors consumed
- D Bernard-Soulier syndrome — platelet GPIb deficiency causing mucocutaneous bleeding
Correct answer: A. Hemorrhagic disease of newborn (Vitamin K deficiency bleeding) — deficiency of factors II, VII, IX, X
Explanation
Neonatal vitamin K deficiency bleeding (VKDB, previously hemorrhagic disease of newborn) presents on day 2-5 with prolonged PT and aPTT (factors II, VII, IX, X, protein C, S all require vitamin K-dependent γ-carboxylation), normal platelet count, and normal fibrinogen. Mixing studies correct because the defect is factor deficiency, not an inhibitor. Hemophilia A prolongs only aPTT (intrinsic pathway). DIC shows low fibrinogen and thrombocytopenia with elevated D-dimers. Prophylactic vitamin K 1 mg IM at birth prevents VKDB.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.