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Repeated USMLE Questions Step 1- 169




A 3-year- old boy is brought to the emergency room by his mother for vomiting and bloody diarrhea for 4 days. She also noticed low urinary output in the past 2 days. He had no similar attacks in the past and his medical and family histories are unremarkable. On examination, his vital signs are within normal limits, no signs of dehydration, no abdominal tenderness or organomegaly and no rashes or any skin manifestations of hemorrhage or internal disease.

Laboratory tests reveal mild anemia, thrombocytopenia and abundant reticulocytes and schistocytes. Urinalysis reveals red blood cells with no casts. Kidney function tests reveal marked increase in serum urea and creatinine. Coagulation profile is normal. Stool Shiga toxin test is positive for Shiga toxin 2.

What is the most likely diagnosis?

A- Idiopathic thrombocytopenic purpura

B- Thrombocytopenic thrombotic purpura

C- Henoch-Schonlein purpura

D- Hemolytic uremic syndrome

E- Renal stones




The triad of hemolytic anemia, acute kidney failure and thrombocytopenia is characteristic of hemolytic uremic syndrome. Also, positive Shiga toxin is confirmatory for diagnosis of HUS.

The correct answer is D



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