Crigler-Najjar syndrome



Crigler-Najjar syndrome

Gastrointestinal system

Gastrointestinal system


Crigler-Najjar syndrome


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USMLE® Step 1 questions

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Crigler-Najjar syndrome

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USMLE® Step 1 style questions USMLE

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A 5-month-old female is brought to the pediatrician for evaluation of jaundice that began after a viral upper respiratory tract infection. She was born at 39 weeks gestation to a 27-year-old, gravida 1 para 1, woman via spontaneous vaginal delivery. The patient has been meeting developmental milestones. Family history is noncontributory. Physical examination shows scleral icterus and diffuse jaundice. Abdominal and neurological exams are unremarkable. Blood testing is performed and reveals the following:  
Laboratory value  Result 
Hemoglobin  13.9 mg.dL 
 Leukocyte count  6,800/mm3 
 Total bilirubin  12.7 mg/dL 
 Conjugated bilirubin  0.3 mg/dL 
 Alanine  aminotransferase  15 U/L 
 Aspartate  aminotransferase  16 U/L 
Phenobarbital is administered, and repeat total serum bilirubin is measured at 7 mg/dL. Which of the following best describes the cause of this patient’s condition?

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Crigler-Najjar syndrome p. 402, 403

presentation p. 718

Jaundice p. 402

Crigler-Najjar syndrome p. 718

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Crigler-Najjar syndrome is an inherited disorder that affects the ability to break down bilirubin, a pigment produced when red blood cells are broken down. Crigler-Najjar syndrome is caused by the absence (type I) or reduced activity (type II) of the enzyme UDP-glucuronosyltransferase, and people having this disease present with high levels of bilirubin in their blood, which can cause yellowing of the skin and eyes (jaundice), dark urine, lightheadedness, confusion, and coma. The severity of symptoms varies among people with this condition.


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