Most Likely Diagnosis: Hemophilia B (Factor IX Deficiency)
The most likely diagnosis is Hemophilia B (Factor IX deficiency), which is clinically indistinguishable from Factor VIII deficiency (Hemophilia A) based on the presentation of umbilical cord stump bleeding, prolonged PTT, and normal platelets. 1
Diagnostic Reasoning
Laboratory Pattern Analysis
The combination of 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 1. This laboratory pattern is the hallmark of hemophilia, where:
- Prolonged PTT reflects intrinsic pathway dysfunction 1
- Normal platelets explicitly excludes ITP, which by definition requires thrombocytopenia 1
- Normal PT (implied) would distinguish this from vitamin K deficiency, which prolongs both PT and PTT 2
Clinical Presentation
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. This presentation should immediately raise suspicion for inherited bleeding disorders, particularly hemophilia 4, 3.
Why Each Answer Option
A. Hemophilia B (Factor IX Deficiency) - CORRECT
- Produces prolonged PTT, normal platelets, and umbilical stump bleeding 1
- Classic neonatal presentation with persistent bleeding from umbilical cord 3
- Requires specific factor IX assay for definitive diagnosis 1
B. ITP - INCORRECT
- Definitively ruled out by normal platelet count 1
- ITP by definition presents with thrombocytopenia 5
- Would not cause prolonged PTT 5
C. Von Willebrand Disease - INCORRECT
- Not reliably detected by PTT screening 1
- Typically does not cause severe umbilical stump bleeding in newborns 1
- Would show abnormal platelet function testing in severe cases 6
D. Factor VIII Deficiency (Hemophilia A) - EQUALLY LIKELY
- Produces an identical laboratory and clinical picture to Hemophilia B 1
- Both present with prolonged PTT, normal PT, normal platelets, and umbilical stump bleeding 1
- Cannot be distinguished without specific factor assays 1
Critical Diagnostic Steps
Immediate evaluation should include:
- Verify vitamin K administration at birth - VKDB must be excluded first as it is treatable and would prolong both PT and PTT 2
- Obtain PT measurement - If PT is also prolonged, vitamin K deficiency is more likely 2
- Order specific factor assays - Factor VIII and Factor IX levels are required to distinguish Hemophilia A from Hemophilia B 1
Important Clinical Pitfalls
Common Diagnostic Errors
Do not assume ITP based on bleeding alone - Normal platelets completely exclude this diagnosis 1. The presence of prolonged PTT with normal platelets points to a coagulation factor deficiency, not a platelet disorder 5.
Do not miss vitamin K deficiency - This is the most common cause of umbilical stump bleeding with prolonged coagulation times in newborns and should be excluded first 2. However, vitamin K deficiency would typically prolong both PT and PTT, not PTT alone 2.
Factor XIII deficiency consideration - While rare, Factor XIII deficiency presents with delayed umbilical cord separation and bleeding but has normal PT, PTT, and platelets 6. The prolonged PTT in this case rules out Factor XIII deficiency 6.
Management Implications
High index of suspicion for inherited bleeding disorders is warranted in every neonate with bleeding from the umbilical stump, especially with prolonged PTT 4. Prompt diagnosis and adequate factor replacement therapy are critical for good outcomes 4, 3.