Vitamin K Deficiency
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 presented is pathognomonic for Vitamin K deficiency:
Prolonged PT and aPTT together indicate deficiency of factors in the common pathway (factors II, X, V) and both extrinsic (factor VII) and intrinsic pathways (factors IX, VIII), which is the hallmark of Vitamin K deficiency affecting factors II, VII, IX, and X 1, 2
Normal bleeding time excludes platelet dysfunction and von Willebrand disease, as these conditions would prolong bleeding time due to impaired primary hemostasis 3, 4
Umbilical bleeding is a classic presentation of Vitamin K deficiency bleeding (VKDB), particularly the early or classical form occurring in the first week of life 5, 6
Why Not the Other Options
Hemophilia A is excluded because:
- Hemophilia A (factor VIII deficiency) would prolong only the aPTT, not the PT, since factor VIII is part of the intrinsic pathway only 1, 4
- The PT would remain normal in isolated factor VIII deficiency 3
- The simultaneous prolongation of both PT and aPTT rules out hemophilia 1
Von Willebrand disease is excluded because:
- Von Willebrand disease typically presents with prolonged bleeding time due to impaired platelet adhesion 4
- The bleeding time is explicitly normal in this case 3
- While severe von Willebrand disease can prolong aPTT (due to low factor VIII), it would not typically prolong PT 4
Clinical Context of Vitamin K Deficiency
Vitamin K deficiency bleeding (VKDB) is classified by timing:
- Early VKDB: <24 hours (often maternal drug-related)
- Classical VKDB: days 1-7 (most common, related to inadequate prophylaxis)
- Late VKDB: >1 week to 6 months (often associated with cholestasis or malabsorption) 5, 6
Umbilical bleeding specifically is a recognized warning sign of VKDB that should prompt immediate investigation and treatment 5, 6
Diagnostic Confirmation
The diagnosis is confirmed by:
- Rapid correction of PT/aPTT within 30 minutes to 2-4 hours after vitamin K administration 2, 5
- Cessation of bleeding following vitamin K replacement 5, 6
- Detection of elevated PIVKA-II (protein induced by vitamin K absence) levels, though this is not routinely available 6, 7
Management Approach
Immediate treatment consists of:
- Vitamin K 1 mg subcutaneously or intramuscularly for treatment of hemorrhagic disease of the newborn 2
- Higher doses may be necessary if maternal anticoagulant exposure occurred 2
- If bleeding is excessive, whole blood or component therapy may be indicated concurrently, though this does not correct the underlying disorder 2
Expected response:
- Prothrombin time should shorten within 2-4 hours 2
- Failure to respond indicates another diagnosis or coagulation disorder 2
Prevention Considerations
Standard prophylaxis recommendations:
- The American Academy of Pediatrics recommends 0.5 to 1 mg vitamin K intramuscularly within one hour of birth for all newborns 2
- Intramuscular prophylaxis is more effective than single oral dose in preventing late VKDB 5, 6
- Multiple oral doses (daily or weekly) may provide protection comparable to intramuscular administration 5, 6
Critical Pitfall to Avoid
Do not delay treatment while awaiting confirmatory testing. In a bleeding newborn with prolonged PT and aPTT but normal fibrinogen and platelet count, empiric vitamin K administration is both diagnostic and therapeutic 2, 5. The rapid response to vitamin K (within 30 minutes to 4 hours) confirms the diagnosis retrospectively 5, 6.