Match the following clinical scenarios of patients presenting with thrombocytopenia to the… — USMLE Step 2 CK

Match the following clinical scenarios of patients presenting with thrombocytopenia to the most likely underlying diagnosis.

A 32-year-old woman presents with petechiae and mucosal bleeding. Laboratory studies show a platelet count of $18,000/\mu L$ . Prothrombin time, activated partial thromboplastin time, and peripheral blood smear are unremarkable.Immune thrombocytopenia (ITP)
A 45-year-old man presents with fever, acute confusion, and a new-onset seizure. Labs reveal a platelet count of $24,000/\mu L$ , hemoglobin of $8.2 \text{ g/dL}$ , and serum creatinine of $2.5 \text{ mg/dL}$ . A peripheral smear shows numerous schistocytes.Thrombotic thrombocytopenic purpura (TTP)
A 65-year-old woman recovering from a total knee arthroplasty develops a swollen, painful right calf on postoperative day 6. Her platelet count has decreased from $210,000/\mu L$ on admission to $95,000/\mu L$ today.Heparin-induced thrombocytopenia (HIT)
A 29-year-old woman at 36 weeks gestation develops abruptio placentae and severe postpartum hemorrhage. Labs show a platelet count of $45,000/\mu L$ , prolonged prothrombin time, prolonged activated partial thromboplastin time, and elevated D-dimer.Disseminated intravascular coagulation (DIC)

Cevap

The correct matches are based on specific laboratory and clinical signatures: Scenario 1 represents Immune thrombocytopenia (ITP); Scenario 2 represents Thrombotic thrombocytopenic purpura (TTP); Scenario 3 represents Heparin-induced thrombocytopenia (HIT); and Scenario 4 represents Disseminated intravascular coagulation (DIC).

Each thrombocytopenic disorder has a distinct clinical and laboratory signature. ITP is a diagnosis of exclusion characterized by isolated thrombocytopenia. TTP presents with microangiopathic hemolytic anemia and end-organ damage due to ADAMTS13 deficiency. HIT presents with a paradoxical prothrombotic state 5-10 days after heparin exposure due to antibodies against the heparin-PF4 complex. DIC involves systemic activation of coagulation and consumption of factors, leading to prolonged PT/aPTT and elevated fibrin split products.

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Analyze the first scenario for isolated lab abnormalities.

The patient has severe thrombocytopenia but normal PT, aPTT, and peripheral smear.

Ruling out consumptive coagulopathy and microangiopathic processes points to peripheral platelet destruction (ITP).

Evaluate the second scenario for the classic TTP pentad.

The patient exhibits fever, neurologic symptoms, thrombocytopenia, renal failure, and schistocytes.

This combination of microangiopathic hemolytic anemia and multiorgan involvement is diagnostic for TTP.

Examine the third scenario for temporal clues and paradoxical findings.

The patient has a 50% platelet drop 6 days post-surgery with a new prothrombotic event (DVT).

Post-surgical patients receive heparin prophylaxis; the specific timeline and paradoxical thrombosis identify HIT.

Assess the fourth scenario for broad coagulation system failure.

The patient has an obstetric trigger (abruption) followed by bleeding, low platelets, prolonged PT/aPTT, and elevated D-dimer.

Widespread factor consumption and fibrinolysis confirm DIC.

Anahtar Kavram

Differential diagnosis of thrombocytopenia based on clinical presentation, coagulation panels, and peripheral blood smear findings.

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