What is the most likely cause of bleeding from the umbilicus in a newborn with prolonged activated partial thromboplastin time (aPTT) and prothrombin time (PT) and a normal bleeding time?

Vitamin K Deficiency

The most likely cause is B) Vitamin K deficiency. The combination of prolonged aPTT and PT with normal bleeding time in a newborn with umbilical bleeding is virtually diagnostic of vitamin K deficiency bleeding (VKDB), and this diagnosis must be excluded first before considering inherited bleeding disorders. 1, 2

Why Vitamin K Deficiency is the Answer

Vitamin K deficiency affects multiple coagulation factors simultaneously (II, VII, IX, and X) because all are vitamin K-dependent, which explains why both PT and aPTT are prolonged. 1, 2 This is the key distinguishing feature that separates it from the other options.

Laboratory Pattern Analysis

• Prolonged PT and aPTT together indicate deficiency of factors in both the common pathway and the extrinsic/intrinsic pathways, which is the hallmark pattern of vitamin K deficiency. 1
• Normal bleeding time excludes platelet dysfunction and von Willebrand disease, as these conditions would prolong bleeding time due to impaired primary hemostasis. 1
• A prolonged PT with normal fibrinogen and platelet count is almost diagnostic of VKDB in a bleeding infant. 1

Clinical Context

• Umbilical stump bleeding is a classic presentation of vitamin K deficiency in newborns, along with bleeding from circumcision, generalized ecchymoses, and intramuscular hemorrhages. 1
• The American Academy of Pediatrics recommends that vitamin K deficiency is the most likely cause of umbilical stump bleeding with prolonged coagulation times in newborns. 2

Why NOT the Other Options

A) Hemophilia A is Excluded

• Hemophilia A would prolong only the aPTT, not the PT, since factor VIII is part of the intrinsic pathway only. 1, 2
• Factor VIII deficiency would leave PT normal, which contradicts the laboratory findings in this case. 3
• The absence of family history strongly argues against inherited hemophilia, which follows X-linked inheritance patterns. 2

C) von Willebrand Disease is Excluded

• Von Willebrand disease typically presents with prolonged bleeding time due to impaired platelet adhesion, and the bleeding time is explicitly normal in this case. 1
• Von Willebrand disease would show abnormal platelet function testing, which is not present here. 3

Diagnostic Confirmation and Management

Immediate Action

• Administer 1 mg vitamin K intramuscularly or intravenously immediately while awaiting confirmatory laboratory correction. 1, 4
• The FDA label recommends 0.5 to 1 mg IM within one hour of birth for prophylaxis, and 1 mg SC or IM for treatment of hemorrhagic disease of the newborn. 4

Expected Response

• Expect PT/aPTT correction within 2-4 hours if VKDB is the diagnosis, as this rapid response confirms the diagnosis retrospectively. 2, 4
• A prompt response (shortening of the prothrombin time in 2 to 4 hours) following administration of vitamin K is usually diagnostic of hemorrhagic disease of the newborn. 4

If No Response

• If coagulopathy does not correct with vitamin K within 2-4 hours, then pursue specific factor assays (Factor VIII and IX levels) to evaluate for inherited hemophilia or other bleeding disorders. 2
• Failure to respond indicates another diagnosis or coagulation disorder. 4

Additional Considerations

• Verify whether vitamin K prophylaxis was given at birth, as breast-feeding without vitamin K prophylaxis is the primary risk factor for VKDB. 2
• Measurement of PIVKA-II (proteins induced by vitamin K absence) can provide additional confirmation if the diagnosis remains uncertain. 1, 2
• For life-threatening bleeding, consider FFP 10-20 mL/kg for immediate factor replacement while awaiting vitamin K effect, though this does not address the underlying deficiency. 1