A newborn male with a suspected clot retraction defect has normal PFA-100, normal ristocetin aggregation, normal ADP/collagen/epinephrine aggregation, but a prolonged aPTT. These results are characteristic of which condition?

• A. von Willebrand disease
• B. Glanzmann thrombasthenia
• C. Storage pool disease
• D. Hemophilia A or B

Answer: (D)

When platelet function tests are normal but the aPTT is prolonged, the issue is in the intrinsic coagulation pathway rather than in primary hemostasis. Normal PFA-100 and normal ristocetin aggregation indicate platelet adhesion/aggregation is functioning and not affected by von Willebrand disease or platelet receptor defects. Normal aggregation with ADP, collagen, and epinephrine further supports intact platelet function. The key abnormality is the prolonged aPTT, which points to a deficiency or inhibition within the intrinsic pathway factors (such as factor VIII or IX). In a newborn male, the classic intrinsic pathway defects are hemophilia A (factor VIII deficiency) and hemophilia B (factor IX deficiency). Thus this pattern is most consistent with Hemophilia A or B.