Vitamin K Deficiency is the Most Likely Diagnosis
The most likely cause of umbilical bleeding in this newborn with prolonged aPTT and PT but normal bleeding time is Vitamin K deficiency (Answer B).
Laboratory Pattern Analysis
The coagulation profile in this case is pathognomonic for vitamin K deficiency:
Prolonged PT and aPTT together indicate deficiency of factors in both the extrinsic/intrinsic and common pathways, which is the hallmark of vitamin K deficiency affecting factors II, VII, IX, and X simultaneously 1.
Normal bleeding time definitively excludes platelet dysfunction and von Willebrand disease, as these conditions would prolong bleeding time due to impaired primary hemostasis 1.
A prolonged PT with normal fibrinogen and platelet count is almost diagnostic of vitamin K deficiency bleeding (VKDB) in a bleeding infant 1, 2.
Why Not the Other Options?
Hemophilia A (Answer A) is Excluded:
- Hemophilia A would prolong only the aPTT, not the PT, since factor VIII deficiency affects only the intrinsic pathway 1.
- The simultaneous prolongation of both PT and aPTT rules out isolated factor VIII deficiency 3.
Von Willebrand Disease (Answer C) is Excluded:
- Von Willebrand disease typically presents with prolonged bleeding time due to impaired platelet adhesion, and the bleeding time is explicitly normal in this case 1, 4.
- Severe von Willebrand disease might show prolonged aPTT, but would not present with isolated umbilical bleeding and normal bleeding time 4.
Clinical Context Supporting Vitamin K Deficiency
Umbilical stump bleeding is a classic presentation of vitamin K deficiency in newborns, along with bleeding from circumcision, generalized ecchymoses, and intramuscular hemorrhages 1.
Vitamin K deficiency affects multiple coagulation factors simultaneously because factors II, VII, IX, and X are all vitamin K-dependent 1, 5.
The absence of vitamin K prophylaxis at birth is a significant risk factor for VKDB, and not all states or institutions mandate vitamin K administration 1.
Breast-feeding is a primary risk factor for VKDB, as breast milk contains insufficient vitamin K 1, 2.
Diagnostic Confirmation
The diagnosis is confirmed by rapid correction of PT/aPTT within 30 minutes to 2-4 hours after vitamin K administration 1, 5, 2.
A prompt response (shortening of the prothrombin time in 2 to 4 hours) following administration of vitamin K is usually diagnostic of hemorrhagic disease of the newborn 5.
Failure to respond to vitamin K indicates another diagnosis or coagulation disorder 5.
Immediate Management
Administer 1 mg vitamin K intramuscularly or intravenously immediately while awaiting confirmatory laboratory correction 1, 5.
For treatment of hemorrhagic disease of the newborn, vitamin K 1 mg should be given either subcutaneously or intramuscularly 5.
Consider fresh-frozen plasma for immediate factor replacement in life-threatening bleeding 1.
Whole blood or component therapy may be indicated if bleeding is excessive, but this does not correct the underlying disorder and vitamin K should be given concurrently 5.
Critical Pitfall to Avoid
Always verify whether vitamin K prophylaxis was administered at birth, as compliance varies and some institutions/states do not mandate it 1.
Be alert to mild bleeding in newborns as warning signs, as prophylaxis with 1 mg of intramuscular vitamin K at birth may occasionally be insufficient to prevent late VKDB 6, 2.