Differential Diagnosis for Prolonged PTT Corrected by Fresh Normal Plasma

• Single Most Likely Diagnosis

  • C. Deficiency of factors XII, XI, IX, or VIII: This is the most likely diagnosis because the correction of the prolonged PTT after addition and incubation with fresh normal plasma suggests a deficiency of one of the factors in the intrinsic pathway (factors XII, XI, IX, or VIII) rather than an inhibitor, which would not be corrected by the addition of normal plasma.

• Other Likely Diagnoses

  • B. Inhibitor against factor I, V, or VIII: Although less likely given the correction with normal plasma, an inhibitor against one of these factors could potentially cause a prolonged PTT. However, inhibitors typically would not correct with mixing studies unless the inhibitor's effect is overwhelmed by a large amount of normal plasma, which is less common.
  • A. Deficiency of factor II, VII, IX, and/or X: While a deficiency in these factors (especially IX) could lead to a prolonged PTT, the fact that PT is normal makes a deficiency in factors II, VII, or X less likely since these factors are also part of the extrinsic pathway (VII) or common pathway (II and X), which would affect PT.

• Do Not Miss Diagnoses

  • D. Inhibitor against factors XII, XI, IX, of VIII: Although the correction with normal plasma makes this less likely, certain inhibitors (like lupus anticoagulants) can sometimes correct in mixing studies, especially if the inhibitor's effect is not very strong. Missing an inhibitor could lead to inappropriate treatment and significant clinical consequences.
  • Acquired bleeding disorders: Conditions such as disseminated intravascular coagulation (DIC) or liver disease could lead to complex coagulopathy presentations, including prolonged PTT. While these would likely affect both PT and PTT, in early or mild cases, PTT might be more significantly affected.

• Rare Diagnoses

  • Factor XIII deficiency: This is a rare bleeding disorder that might not significantly prolong PTT but could lead to clinical bleeding. It's less likely to be diagnosed through PTT prolongation alone but should be considered in patients with unexplained bleeding.
  • Von Willebrand disease: Certain types of von Willebrand disease could lead to a prolonged PTT due to decreased factor VIII activity. However, this diagnosis would typically be suspected based on clinical presentation and specific von Willebrand factor assays rather than PTT correction with normal plasma alone.