What is the most likely cause of a newborn's bleeding from the umbilical stump, delayed separation of the umbilical cord, and coagulation study results showing prolonged Prothrombin Time (PT) and Partial Thromboplastin Time (PTT) with a normal platelet count?

Vitamin K Deficiency (Answer: C)

The most likely diagnosis is vitamin K deficiency, given the combination of umbilical stump bleeding, delayed cord separation, prolonged PT and PTT, normal platelet count, and delayed clot time in a newborn. 1, 2

Clinical Reasoning

Why Vitamin K Deficiency is the Answer

• Vitamin K deficiency affects multiple coagulation factors simultaneously (factors II, VII, IX, and X), which explains why both PT and PTT are prolonged 2, 3
• Umbilical stump bleeding is a classic presentation of vitamin K deficiency bleeding (VKDB) in newborns 1, 2, 3
• The laboratory pattern of prolonged PT and aPTT together with normal platelets is almost diagnostic of VKDB in a bleeding infant 2
• Not all states require vitamin K administration at birth, making VKDB still possible despite widespread prophylaxis programs 1, 2

Why the Other Options Are Incorrect

Hemophilia A (Option A) is excluded because:

• Factor VIII deficiency would prolong only the PTT, not the PT, since factor VIII is part of the intrinsic pathway only 2, 4
• The question explicitly states both PT and PTT are prolonged 2

Von Willebrand Disease (Option B) is excluded because:

• VWD typically presents with prolonged bleeding time due to impaired platelet adhesion 2, 4
• VWD would show abnormal platelet function testing, not just prolonged PT/PTT 4
• ICH in VWD is extremely rare, and umbilical stump bleeding is not a classic presentation 1

Thrombocytopenia (Option D) is excluded because:

• The question explicitly states platelet count is normal 1, 2

Diagnostic Confirmation

The diagnosis is confirmed by rapid correction of PT/PTT within 2-4 hours after vitamin K administration 2, 3:

• A prompt response (shortening of prothrombin time in 2-4 hours) following vitamin K administration is usually diagnostic of hemorrhagic disease of the newborn 3
• Failure to respond indicates another diagnosis or coagulation disorder 3

Measurement of proteins induced by vitamin K absence (PIVKA) can confirm the diagnosis in patients already treated with vitamin K or fresh-frozen plasma 1, 2

Immediate Management

Administer vitamin K 1 mg intramuscularly or intravenously immediately while awaiting confirmatory laboratory correction 2, 3:

• For treatment of hemorrhagic disease of the newborn, vitamin K 1 mg should be given either subcutaneously or intramuscularly 3
• Higher doses may be necessary if the mother has been receiving oral anticoagulants 3

Consider fresh-frozen plasma for immediate factor replacement if bleeding is life-threatening or excessive 2, 3

Important Clinical Caveat

Factor XIII deficiency can present similarly with umbilical stump bleeding and delayed cord separation, but has normal PT, PTT, and platelet count 4, 5, 6. However, the question explicitly states PT and PTT are prolonged, which rules out factor XIII deficiency and confirms vitamin K deficiency as the diagnosis 2, 4.