Vitamin K Deficiency is the Most Likely Diagnosis
In a newborn presenting with umbilical stump bleeding and prolonged aPTT, vitamin K deficiency is the most likely cause, particularly if PT is also prolonged. 1
Diagnostic Reasoning
Laboratory Pattern Analysis
The key to this diagnosis lies in understanding the coagulation cascade abnormalities:
- Prolonged PT and aPTT together indicate deficiency of factors in the common pathway (factors II, VII, IX, and X), which is the hallmark pattern of vitamin K deficiency 2
- Vitamin K deficiency affects multiple coagulation factors simultaneously because factors II, VII, IX, and X are all vitamin K-dependent 1, 3
- In a bleeding infant, a prolonged PT with normal fibrinogen and platelet count is almost diagnostic of vitamin K deficiency bleeding (VKDB) 1, 3
Why Not Hemophilia A?
Hemophilia A is definitively excluded by the laboratory pattern described:
- Hemophilia A (factor VIII deficiency) prolongs only the aPTT, never the PT, because factor VIII is exclusively part of the intrinsic pathway 2, 4
- The presence of prolonged PT in addition to prolonged aPTT rules out hemophilia A 2
- Hemophilia A would show normal PT with isolated aPTT prolongation 5
Clinical Context Supporting Vitamin K Deficiency
Timing and Presentation
- Umbilical stump bleeding is a classic presentation of vitamin K deficiency in newborns, along with bleeding from circumcision, generalized ecchymoses, and intramuscular hemorrhages 1
- VKDB can be classified by timing: early (<24 hours), classical (days 1-7), and late (>1 week to <6 months) 3, 6
- Umbilical stump bleeding typically occurs in the classical or late forms of VKDB 3
Risk Factors to Assess
- Breast-feeding is the primary risk factor for VKDB, as breast milk contains insufficient vitamin K 3, 6, 7
- Determine if vitamin K prophylaxis was administered at birth—not all states require vitamin K administration 1
- Secondary VKDB occurs with cholestasis, hepatobiliary disease, malabsorption, or poor oral intake 1, 6
Diagnostic Confirmation
Immediate Testing
- The diagnosis is confirmed by rapid correction of PT/aPTT within 30 minutes to 2-4 hours after vitamin K administration 2, 3
- Cessation of bleeding after vitamin K administration is confirmatory 3, 6
- In patients already treated with vitamin K or fresh-frozen plasma, measurement of proteins induced by vitamin K absence (PIVKA) can confirm the diagnosis 1
Laboratory Findings Expected
- Prolonged PT and aPTT for age 1, 8
- Normal or increased fibrinogen level 1, 3
- Normal platelet count 1, 3
- Presence of acarboxy proteins (undercarboxylated vitamin K-dependent factors) 6
Immediate Management
Administer vitamin K immediately while awaiting confirmatory laboratory correction:
- Give 1 mg vitamin K intramuscularly or intravenously 3, 6
- Expect PT shortening within 30 minutes and clinical improvement within 2-4 hours 3, 6
- If life-threatening bleeding (especially intracranial), consider fresh-frozen plasma for immediate factor replacement while vitamin K takes effect 1
Critical Pitfalls to Avoid
- Do not delay vitamin K administration while pursuing extensive coagulation workup—the rapid response to vitamin K is both therapeutic and diagnostic 3, 6
- Do not assume vitamin K prophylaxis was given at birth—verify administration, as compliance varies and some institutions/states do not mandate it 1
- Recognize warning signs of late VKDB: prolonged jaundice, failure to thrive, feeding problems, or minor bleeding episodes that precede major hemorrhage 1, 3
- Intracranial bleeding is the most serious complication of VKDB and carries high morbidity and mortality—maintain high suspicion in any bleeding newborn 3, 6