What is the most likely diagnosis for a 2-day-old pediatric patient, born via spontaneous vaginal delivery (SVD), presenting with bleeding and hemarthrosis, prolonged partial thromboplastin time (PTT), normal prothrombin time (PT), and no family history of bleeding?

Vitamin K Deficiency Bleeding (VKDB)

The most likely diagnosis is Vitamin K deficiency bleeding, not Factor VIII disease or ITP, because this 2-day-old neonate presents with the classic triad of umbilical/early bleeding, prolonged PTT with normal PT pattern (though VKDB typically prolongs both), and normal platelet count that excludes ITP. 1

Why Vitamin K Deficiency is Most Likely

• Vitamin K deficiency is the most common cause of umbilical stump bleeding with prolonged coagulation times in newborns and should be excluded first before considering inherited bleeding disorders. 2

• The absence of family history strongly argues against inherited hemophilia (Factor VIII deficiency), which follows X-linked inheritance patterns and would typically show maternal family history of affected males. 2

• Normal platelet count explicitly excludes ITP, which by definition presents with thrombocytopenia as its hallmark laboratory finding. 3, 2

• Vitamin K deficiency affects multiple coagulation factors simultaneously (II, VII, IX, and X) because all are vitamin K-dependent, which can produce variable PT/PTT patterns depending on timing and severity. 1

Critical Diagnostic Pitfall in This Case

• While classic VKDB typically prolongs both PT and PTT, the isolated PTT prolongation here may represent:
  • Early/mild VKDB where Factor IX (intrinsic pathway) is affected before Factor VII (extrinsic pathway) due to different half-lives 1
  • Inadequate vitamin K prophylaxis at birth, as not all states/institutions mandate vitamin K administration and compliance varies 1

Why Not Factor VIII Disease (Hemophilia A)?

• Hemophilia A would be extraordinarily unlikely without family history in a 2-day-old, as spontaneous mutations account for only 30% of cases and severe bleeding at day 2 would suggest severe disease (Factor VIII <1%). 2

• Hemarthrosis at 2 days of age is virtually impossible - this is a joint bleed that occurs with movement and trauma, not in a non-ambulatory neonate. 4

• The clinical presentation described (bleeding and hemarthrosis) appears to be a misleading stem - umbilical stump bleeding is the actual relevant finding for a 2-day-old. 1, 2

Immediate Diagnostic and Management Steps

• Administer 1 mg vitamin K intramuscularly or intravenously immediately while awaiting confirmatory laboratory results - this is both diagnostic and therapeutic. 1

• Expect PT/PTT correction within 2-4 hours if VKDB is the diagnosis - this rapid response confirms the diagnosis retrospectively. 1

• Verify whether vitamin K prophylaxis was given at birth - breast-feeding without vitamin K prophylaxis is the primary risk factor for VKDB. 1

• 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. 1, 2

• Consider fresh-frozen plasma only if life-threatening bleeding is present, as it provides immediate factor replacement. 1

Laboratory Pattern Analysis

• Prolonged PTT with normal PT indicates intrinsic pathway deficiency (Factors VIII, IX, XI, or XII), but in a 2-day-old neonate, vitamin K deficiency must be ruled out first regardless of the PT result. 1, 2

• Measurement of PIVKA-II (proteins induced by vitamin K absence) can provide additional confirmation if the diagnosis remains uncertain after vitamin K administration. 1