View source for WBR271

{{WBRQuestion
|QuestionAuthor={{Sapan}}
|ExamType=USMLE Step 3
|MainCategory=Community Medical Health Center, Primary Care Office
|SubCategory=Genitourinary, Genitourinary, Hematology, Pediatrics
|MainCategory=Community Medical Health Center, Primary Care Office
|SubCategory=Genitourinary, Genitourinary, Hematology, Pediatrics
|MainCategory=Community Medical Health Center, Primary Care Office
|SubCategory=Genitourinary, Genitourinary, Hematology, Pediatrics
|MainCategory=Community Medical Health Center, Primary Care Office
|MainCategory=Community Medical Health Center, Primary Care Office
|SubCategory=Genitourinary, Genitourinary, Hematology, Pediatrics
|MainCategory=Community Medical Health Center, Primary Care Office
|SubCategory=Genitourinary, Genitourinary, Hematology, Pediatrics
|MainCategory=Community Medical Health Center, Primary Care Office
|SubCategory=Genitourinary, Genitourinary, Hematology, Pediatrics
|MainCategory=Community Medical Health Center, Primary Care Office
|SubCategory=Genitourinary, Genitourinary, Hematology, Pediatrics
|MainCategory=Community Medical Health Center, Primary Care Office
|MainCategory=Community Medical Health Center, Primary Care Office
|SubCategory=Genitourinary, Genitourinary, Hematology, Pediatrics
|Prompt=A 6-year-old child is brought to office because of a sudden onset of irritability, weakness, and pallor. The father provides history that both of his children have been experiencing episodes of vomiting and diarrhea. His physical examination reveals a blood pressure of 116/82, dry mucus membranes, petechiae, and diffuse abdominal pain. The following laboratory work is obtained:

*Urinalysis: microscopic hematuria and proteinuria
*Blood urea nitrogen (BUN)/creatinine (Cr): 20/1.0 mg/dL
*Hemoglobin: 7 g/dL
*Peripheral blood smear: fragmented RBCs
*Prothrombin time (PT), partial thromboplastin time (PTT): normal
*Coombs' test: negative

What is the most likely diagnosis?
|Explanation=HUS (Hemolytic Uraemic Syndrome) is the combination of a microangiopathic hemolytic anemia and acute renal failure. It is commonly associated with E. coli O157/H7 gastroenteritis. HUS is one of the most common causes of acquired renal failure in children.

EDUCATIONAL OBJECTIVE: HUS is triad of gastroenteritis, microangiopathic hemolytic anemia and acute renal failure.
|AnswerA=Idiopathic thrombocytopenic purpura
|AnswerAExp=Incorrect- Idiopathic thrombocytopenic purpura is a bleeding disorder in which the immune system destroys platelets, which are necessary for normal blood clotting. Persons with the disease have too few platelets in the blood. But findings of gastroenteritis and acute renal failure are more suggestive of HUS.
|AnswerB=Henoch Schonlein Purpura
|AnswerBExp=Incorrect- Purpura, arthritis and abdominal pain are known as the "classic triad" of Henoch–Schönlein purpura.But finding of acute renal failure are more suggestive of HUS.
|AnswerC=Evans syndrome
|AnswerCExp=Incorrect- Evans syndrome is an autoimmune disease in which an individual's antibodies attack their own red blood cells and platelets. Both of these events may occur simultaneously or one may follow on from the other. But findings of gastroenteritis and acute renal failure are more suggestive of HUS.
|AnswerD=Meningococcemia
|AnswerDExp=Incorrect- Meningococcemia, like many gram-negative blood infections, can cause disseminated intravascular coagulation (DIC), which is the inappropriate clotting of blood within the vessels. DIC can cause ischemic tissue damage when upstream thrombus obstructs blood flow and haemorrhage because clotting factors are exhausted. But normal PT and PTT findings exclude this as a possibility.
|AnswerE=Hemolytic Uraemic Syndrome
|AnswerEExp=Correct- See explanation
|RightAnswer=E
|Approved=Yes
}}