Vitamin K Deficiency is the Most Likely Diagnosis
In a newborn with umbilical bleeding and prolonged PT and aPTT with normal bleeding time, vitamin K deficiency is the most likely diagnosis. This laboratory pattern—simultaneous prolongation of both PT and aPTT—indicates deficiency of multiple coagulation factors in the common pathway, which is pathognomonic for vitamin K deficiency affecting factors II, VII, IX, and X 1.
Why Vitamin K Deficiency Fits Perfectly
Umbilical stump bleeding is a classic presentation of vitamin K deficiency bleeding (VKDB) in newborns, along with bleeding from circumcision and generalized ecchymoses 1.
The laboratory pattern is diagnostic: Prolonged PT and aPTT together indicate deficiency of factors in both the extrinsic/intrinsic pathways and common pathway, which occurs when vitamin K-dependent factors (II, VII, IX, X) are depleted 1, 2.
Normal bleeding time excludes platelet and vascular disorders, confirming this is a coagulation factor problem rather than primary hemostasis dysfunction 1.
Vitamin K deficiency is the single most common cause of combined PT/aPTT prolongation in newborns, particularly when vitamin K prophylaxis was not administered at birth 2.
Why NOT Hemophilia A (Option A)
Hemophilia A would prolong only the aPTT, not the PT, since factor VIII deficiency affects only the intrinsic pathway 1, 3.
The simultaneous prolongation of both PT and aPTT rules out isolated factor VIII deficiency 1.
Why NOT von Willebrand Disease (Option C)
Von Willebrand disease typically presents with prolonged bleeding time due to impaired platelet adhesion, but the bleeding time is explicitly normal in this case 1, 3.
Standard PT/aPTT screening does not reliably detect von Willebrand disease—specific von Willebrand factor assays are required for diagnosis 3.
While von Willebrand disease can present with post-circumcision bleeding, it would not produce this specific laboratory pattern of prolonged PT/aPTT with normal bleeding time 3.
Diagnostic Confirmation
A prolonged PT with normal fibrinogen and platelet count is almost diagnostic of vitamin K deficiency bleeding in a bleeding infant 1.
Rapid correction of PT/aPTT within 30 minutes to 2-4 hours after vitamin K administration confirms the diagnosis 1, 4.
Measurement of proteins induced by vitamin K absence (PIVKA-II) can provide additional confirmation if needed 5, 1.
Immediate Management
Administer vitamin K 1 mg intramuscularly or intravenously immediately while awaiting laboratory confirmation 1, 4.
For significant bleeding, consider fresh frozen plasma for immediate factor replacement while vitamin K takes effect 1, 4.
Expect shortening of prothrombin time within 2-4 hours after vitamin K administration; failure to respond indicates another diagnosis 4, 1.