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Patient Story

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A 4-year-old boy presents to his pediatrician because of swelling over the face, malaise, fatigue, and decreased appetite. On further questioning, his parents state that he appears pale and has reduced urine output. He recently finished a course of antibiotics for bloody diarrhea. On exam, he is found to be hypertensive and pale and has anasarca. Initial laboratory studies show a hemoglobin of 7 g/dL, platelet count of 44,000/mm3, blood urea nitrogen of 39 mg/dL and creatinine of 2.9 mg/dL. Peripheral smear shows the presence of schistocytes and a paucity of platelets (Figures 69-1 and 69-2). He is admitted to the pediatric intensive care unit for hemolytic uremic syndrome. He is treated conservatively with close attention to fluid intake and output, restriction of sodium and fluid intake, and antihypertensive medications as needed. A stool culture obtained at the onset of his bloody diarrhea grows Escherichia coli and is identified as serotype 0157:H7. Hemoglobin declines to 5.2 g/dL for which he is transfused packed red blood cells. Platelet count decreases over the next few days and then improves. He has no evidence of bleeding. Azotemia and oliguria improve over a week, appetite improves and anasarca resolves. He is discharged home with an excellent prognosis for full recovery.

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FIGURE 69-1

Schistocytes (fragmented “helmet” cells) and paucity of platelets, characteristic features of hemolytic uremic syndrome on blood peripheral smear, high magnification. (Used with permission from Megan Nakashima, MD.)

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FIGURE 69-2

Schistocytes (fragmented “helmet” cells) and paucity of platelets, characteristic features of hemolytic uremic syndrome on blood peripheral smear, low magnification. (Used with permission from Megan Nakashima, MD.)

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Introduction

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The hemolytic uremic syndrome (HUS) was first described in 1955 by Gasser et al.1 HUS is a thrombotic microangiopathy characterized by a triad of hemolytic anemia, thrombocytopenia and acute kidney injury.

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Synonyms

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  • Typical HUS is also known as D(+) HUS, Shiga toxin-producing Escherichia coli (STEC) HUS, verocytotoxin producing Escherichia coli (VTEC) HUS, or Shiga-like toxin associated (Stx) HUS.

  • Atypical HUS is also referred to as D(–) HUS and non-Shiga-like toxin associated (non-Stx) HUS.

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Epidemiology

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  • It is the most common cause of renal failure in childhood.2

  • Worldwide, the incidence is 0.2 to 4 cases per 100,000 per year.3

  • It is more common in children under 5 years with an incidence of approximately 6 cases per 100,000 per year.4

  • There is also a geographical variation, with the highest incidence reported in Argentina.5

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Etiology and Pathophysiology

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  • In 2006, the European Study Group for HUS proposed a classification for HUS, thrombotic thrombocytopenic purpura (TTP) and related disorders, which ...

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