Hemophilia B (Factor IX Deficiency)
The most likely diagnosis is Hemophilia B (Factor IX deficiency), given the newborn's continuous umbilical cord stump bleeding, prolonged PTT, and normal platelet count. 1
Diagnostic Reasoning
The clinical presentation and laboratory pattern point definitively toward a coagulation factor deficiency affecting the intrinsic pathway:
- Prolonged PTT with normal platelets indicates a deficiency in the intrinsic or common coagulation pathway (factors VIII, IX, XI, or XII), not a platelet disorder 2
- Umbilical cord stump bleeding is a classic early presentation of severe hemophilia, as this site is particularly vulnerable to bleeding in newborns with coagulation factor deficiencies 1, 3
- Normal platelet count explicitly excludes ITP (option B), which by definition presents with thrombocytopenia 2
Why Each Answer Option Is Correct or Incorrect
Hemophilia B (Factor IX Deficiency) - CORRECT
- Hemophilia B causes isolated PTT prolongation because Factor IX is part of the intrinsic pathway only 4, 5
- Severe hemophilia B (Factor IX activity <1%) presents in the neonatal period with bleeding from the umbilical stump, post-circumcision bleeding, or intracranial hemorrhage 6
- The X-linked inheritance pattern means male newborns are predominantly affected 4, 7
Factor VIII Deficiency (Hemophilia A) - ALSO CORRECT (Option D)
- Factor VIII deficiency produces an identical laboratory and clinical picture to Hemophilia B: prolonged PTT, normal PT, normal platelets, and umbilical stump bleeding 2, 6
- Both Hemophilia A and B are clinically indistinguishable without specific factor assays 5, 6
- Options A and D are essentially the same diagnosis from a clinical standpoint—both are severe hemophilia requiring the same immediate management
ITP - INCORRECT
- ITP is definitively excluded because the platelet count is explicitly normal 2
- ITP presents with thrombocytopenia (low platelet count) and normal PT/PTT 2
- Neonatal ITP from maternal antibody transfer would show low platelets, not prolonged PTT 2
Von Willebrand Disease - INCORRECT
- Von Willebrand disease is not reliably detected by PTT screening and typically does not cause severe umbilical stump bleeding in newborns 2
- Most VWD types present with mucocutaneous bleeding (epistaxis, easy bruising) rather than deep tissue or umbilical bleeding 2
- Severe Type 3 VWD can prolong PTT, but this represents only 1-5% of VWD cases and would require specific von Willebrand factor testing for diagnosis 2
Critical Diagnostic Pitfall
Mild hemophilia (Factor VIII or IX levels 5-40%) may show normal or only minimally prolonged PTT, depending on the reagent sensitivity used 4. However, this newborn has continuous bleeding, indicating severe hemophilia with factor levels <1%, which always produces markedly prolonged PTT 4, 5.
Immediate Next Steps
- Obtain specific factor assays (Factor VIII and Factor IX levels) to distinguish Hemophilia A from Hemophilia B 5, 6
- Administer factor replacement immediately if bleeding is life-threatening, before confirmatory testing returns 6
- Rule out vitamin K deficiency by checking PT—if PT is also prolonged, give vitamin K 1 mg IV/IM immediately, as vitamin K deficiency is more common and easier to treat 1
- Mixing studies (1:1 mix with normal plasma) will show complete correction in factor deficiency versus incomplete correction if an inhibitor is present 5
Why Vitamin K Deficiency Must Be Excluded First
While not listed as an answer option, vitamin K deficiency is actually the most common cause of umbilical stump bleeding with prolonged coagulation times in newborns 1. However, vitamin K deficiency would prolong both PT and PTT because it affects factors II, VII, IX, and X 1, 8. The question states only PTT is prolonged, making hemophilia more likely than vitamin K deficiency.