Differential Diagnosis

The provided lab results show a prolonged bleeding time, normal PT, and significantly prolonged aPTT, with normal thrombin time and fibrinogen levels. Based on these findings, the differential diagnosis can be categorized as follows:

• Single most likely diagnosis

  • Hemophilia A, B, or other intrinsic factor deficiency: The significantly prolonged aPTT with normal PT and bleeding time slightly prolonged (which can be seen in mild cases or due to other factors) points towards a problem with the intrinsic pathway of coagulation, which is characteristic of Hemophilia A or B.

• Other Likely diagnoses

  • Abnormal platelets: Although the primary issue seems to be with the coagulation cascade rather than platelet function (given the significant prolongation of aPTT), abnormal platelet function could contribute to the prolonged bleeding time. However, this would not fully explain the aPTT prolongation.
  • Heparin therapy: Heparin can cause a prolongation of aPTT. However, it would also be expected to affect the thrombin time, which is not significantly prolonged in this case.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

  • Heparin-induced thrombocytopenia (HIT): Although less likely given the lack of significant thrombocytopenia information and the thrombin time being within normal limits, HIT is a condition that could present with prolonged aPTT due to heparin use and is critical not to miss due to its high morbidity and mortality.
  • Disseminated Intravascular Coagulation (DIC): This condition can present with a variety of coagulation abnormalities, including prolonged aPTT. It's a critical diagnosis not to miss due to its severity and the need for prompt treatment.

• Rare diagnoses

  • von Willebrand’s Disease: While von Willebrand's disease can cause a prolonged bleeding time and aPTT (due to its effect on factor VIII), the significant prolongation of aPTT without more specific testing (like von Willebrand factor antigen and activity) makes it less likely compared to other intrinsic pathway deficiencies.
  • Lupus Anticoagulant: This can cause a prolongation of aPTT but is usually seen in the context of other clinical findings suggestive of antiphospholipid syndrome. It's a rare cause of isolated aPTT prolongation without other symptoms.