Match each patient vignette presenting with a complex bleeding or thrombotic complication … — USMLE Step 2 CK

Match each patient vignette presenting with a complex bleeding or thrombotic complication to the most appropriate targeted therapy or management strategy.

A $72$ -year-old man in the outpatient clinic presents with large, spontaneous ecchymoses on his torso over the past $3$ weeks. Vitals are normal. Labs show hemoglobin $11.2 \text{ g/dL}$ , platelets $250,000/\mu\text{L}$ , PT $12 \text{ s}$ , and aPTT $68 \text{ s}$ . A $1:1$ mixing study immediately corrects aPTT to $32 \text{ s}$ , but after $2$ hours of incubation at $37^\circ\text{C}$ , the aPTT prolongs to $55 \text{ s}$ .Administer recombinant factor VIIa or activated prothrombin complex concentrate
A $32$ -year-old woman in the emergency department presents with unilateral leg swelling and pain. She has a history of two first-trimester miscarriages. Vitals are normal. Ultrasound confirms a deep vein thrombosis. Labs show platelets $180,000/\mu\text{L}$ , PT $13 \text{ s}$ , and aPTT $58 \text{ s}$ . A $1:1$ mixing study yields an immediate aPTT of $54 \text{ s}$ . The aPTT normalizes after adding excess exogenous phospholipids.Initiate lifelong therapeutic anticoagulation with a vitamin K antagonist
A $24$ -year-old woman presents for evaluation of lifelong heavy menses and frequent epistaxis. Labs show hemoglobin $10.5 \text{ g/dL}$ , platelets $130,000/\mu\text{L}$ , PT $12 \text{ s}$ , and aPTT $38 \text{ s}$ . Ristocetin cofactor activity is $15\%$ , and VWF antigen is $45\%$ . Platelet aggregometry demonstrates heightened, robust aggregation in response to very low concentrations of ristocetin.Administer von Willebrand factor concentrate and specifically avoid desmopressin (DDAVP)
A $16$ -year-old boy is brought to the clinic for recurrent, severe gingival bleeding. Physical exam shows scattered petechiae. Labs reveal hemoglobin $12.0 \text{ g/dL}$ , platelets $45,000/\mu\text{L}$ with numerous giant platelets on peripheral smear, PT $12 \text{ s}$ , and aPTT $30 \text{ s}$ . Platelet aggregation with ristocetin is absent and does not improve when normal patient plasma is added.Administer platelet transfusions for acute severe bleeding episodes

Answer

Vignette 1 matches 'Administer recombinant factor VIIa or activated prothrombin complex concentrate'. Vignette 2 matches 'Initiate lifelong therapeutic anticoagulation with a vitamin K antagonist'. Vignette 3 matches 'Administer von Willebrand factor concentrate and specifically avoid desmopressin (DDAVP)'. Vignette 4 matches 'Administer platelet transfusions for acute severe bleeding episodes'.

Each correct pairing directly links a highly specific and complex laboratory profile to its exact diagnosis and corresponding life-saving or disease-modifying therapy, requiring multi-step pathophysiologic reasoning.

Step-by-Step Solution

Analyze the mixing study and coagulation profile in the first vignette.

A time-dependent inhibitor is identified, characteristic of an acquired factor VIII autoantibody.

To determine that standard factor VIII replacement will fail and bypassing agents are required.

Evaluate the coagulation profile and clinical history in the second vignette.

A phospholipid-dependent immediate inhibitor is identified in a patient with DVT and miscarriages, diagnosing Antiphospholipid Syndrome.

To identify that lifelong vitamin K antagonist anticoagulation is required for secondary thrombosis prevention.

Assess the platelet aggregometry and VWF studies in the third vignette.

Enhanced aggregation with low-dose ristocetin confirms Type 2B VWD.

To recognize that DDAVP is contraindicated and exogenous VWF concentrate must be utilized.

Analyze the peripheral smear and aggregation studies in the fourth vignette.

Macrothrombocytopenia with absent ristocetin aggregation unresponsive to normal plasma confirms Bernard-Soulier syndrome.

To determine that because the defect is intrinsic to the platelets, platelet transfusion is the definitive therapy.

Key Concept

Interpretation of advanced coagulation assays (immediate vs. incubated mixing studies, phospholipid dependence) and specialized platelet aggregometry is required to diagnose complex acquired and congenital hematologic disorders and select appropriate targeted therapies.

Estimated Time:3m 0s

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