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The mother of a 4-year-old patient calls to report that she noticed he has developed red spots and purplish bruises on both of his legs, some of which are firm and palpable, even though he denies any history of trauma. Moreover, he told his mother that his most recent stool appeared bloody. You ask that they go to the emergency department (ED), where a complete blood count (CBC) reveals that his platelet count is 397 × 109/L. You suspect Henoch-Schönlein purpura (HSP). Which of the following findings would be consistent with your diagnosis?

A. Decreased factor VIII level

B. Wet purpura (purpura in the oral mucosa)

C. Elevated blood pressure

D. Hypofibrinogenemia

E. Prolonged prothrombin time

Answer: C

Patients with HSP may have renal involvement, which may lead to hypertension. Therefore, evaluation of patients suspected of having HSP should include careful attention to vital signs for evidence of renal involvement, including close attention to evidence of hypertension. The petechiae and purpura associated with HSP are characteristically in the lower extremities rather than mucosal. Although patients have petechiae and purpura, the lesions arise from vasculitis and are not due to coagulopathy, so fibrinogen and clotting factor levels and prothrombin time are normal.

You are asked to evaluate a 5-year-old boy with persistently elevated hemoglobin. The p50 (the partial pressure of oxygen at which the patient's hemoglobin is 50% saturated with oxygen) is 20 mm Hg (normal is 26 mm Hg), and his hemoglobin saturation curve is left shifted. This suggests that his polycythemia is due to which of the following?

A. Chuvash polycythemia

B. Presence of a JAK2 mutation

C. Living at high altitude

D. Cyanotic cardiac disease

E. Higher-affinity hemoglobin

Answer: E

A leftward-shifted oxygen dissociation curve and a lower-than-normal p50 are consistent with an increased hemoglobin oxygen affinity. This results in less oxygen release to the tissues and thus a compensatory increase in hemoglobin. Figure ...

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