Examkin

Question

Difficulty: HardHematology and Oncology

Evaluate the following clinical vignettes detailing patients with abnormal coagulation profiles. Match each patient presentation with the most accurate underlying pathophysiologic mechanism.

  • A 22-year-old man undergoes preoperative evaluation. Labs show an isolated prolonged aPTT that fully corrects when mixed 1:1 with normal plasma. PT and platelet count are normal.Intrinsic pathway factor deficiency
  • A 31-year-old woman with recurrent miscarriages presents with deep vein thrombosis. Labs show a prolonged aPTT that does not correct with a 50:50 normal plasma mixing study.Presence of a coagulation inhibitor
  • A 14-year-old girl presents with menorrhagia and frequent epistaxis. Labs reveal a normal platelet count, normal PT, slightly prolonged aPTT, and decreased ristocetin cofactor activity.Defect in platelet-endothelial adhesion
  • A 65-year-old man with metastatic prostate cancer presents with widespread ecchymoses. Labs demonstrate thrombocytopenia, prolonged PT and aPTT, and low fibrinogen.Systemic consumption of coagulation factors and platelets

Answer

The clinical presentations correctly match the following mechanisms: The isolated correcting aPTT reflects an intrinsic pathway factor deficiency. The non-correcting aPTT with thrombosis reflects the presence of a coagulation inhibitor. The mucosal bleeding with decreased ristocetin activity reflects a defect in platelet-endothelial adhesion. The global coagulopathy with thrombocytopenia reflects systemic consumption of coagulation factors and platelets.
Accurate diagnosis of coagulation disorders requires integrating the clinical scenario (bleeding vs. thrombosis, mucosal vs. joint involvement) with targeted laboratory findings. Mixing studies are the critical initial step to differentiate between simple factor deficiencies and the presence of inhibitors. Platelet counts and specific assays, such as ristocetin cofactor, further clarify complex bleeding diatheses by isolating adhesion defects from consumption coagulopathies.

Step-by-Step Solution

1
Analyze the mixing study results for the first two patients.
The first patient's aPTT corrects, indicating a factor deficiency. The second patient's aPTT does not correct, indicating the presence of an inhibitor.
Mixing patient plasma 1:1 with normal plasma provides all necessary coagulation factors. If the aPTT normalizes, it confirms a deficiency. If it remains prolonged, an autoantibody (inhibitor) is present and neutralizing the added factors.
2
Evaluate the clinical presentation and specific lab tests for the adolescent female with mucosal bleeding.
The decreased ristocetin cofactor activity confirms a diagnosis of von Willebrand disease.
Ristocetin induces von Willebrand factor-dependent platelet agglutination. Decreased activity in the setting of normal platelet counts confirms a defect in platelet adhesion rather than primary thrombocytopenia.
3
Assess the global coagulation derangement in the elderly man with malignancy.
Global abnormalities including prolonged PT/aPTT, thrombocytopenia, and hypofibrinogenemia point to Disseminated Intravascular Coagulation (DIC).
Advanced malignancies, particularly mucin-secreting adenocarcinomas and prostate cancer, can trigger systemic activation of the coagulation cascade, rapidly consuming both platelets and coagulation factors.

Key Concept

Interpretation of coagulation panels and mixing studies to identify bleeding and thrombotic disorders
Rate this question

Topics

Hematology and Oncology

More questions from this topic