A 4-week-old boy is brought to the office for a routine well-baby visit. The boy has been exclusively breastfeeding every 2-3 hours and is making 6 or 7 wet diapers a day. His urine has appeared dark yellow, and he has had a few pale-colored stools. His parents also noticed that his skin has appeared yellow for the past 2 weeks, but they were not concerned as they heard from friends that yellow skin is common with breastfeeding. The patient was born full term without complications by vaginal delivery to a primigravida. On physical examination, he is well-appearing with icteric sclerae and jaundice of the head and upper chest. Abdominal examination reveals a mildly enlarged and firm liver. Liver function results are as follows: Which of the following is the most likely mechanism for the patient's presentation?

Question

A 4-week-old boy is brought to the office for a routine well-baby visit.  The boy has been exclusively breastfeeding every 2-3 hours and is making 6 or 7 wet diapers a day.  His urine has appeared dark yellow, and he has had a few pale-colored stools.  His parents also noticed that his skin has appeared yellow for the past 2 weeks, but they were not concerned as they heard from friends that yellow skin is common with breastfeeding.  The patient was born full term without complications by vaginal delivery to a primigravida.  On physical examination, he is well-appearing with icteric sclerae and jaundice of the head and upper chest.  Abdominal examination reveals a mildly enlarged and firm liver.  Liver function results are as follows:  Which of the following is the most likely mechanism for the patient's presentation?

Quizplus · Accepted Answer

11ec160b_3ad7_1c16_9249_2d55a39b2c2d_MD0001_00 Biliary atresia is a progressive, complete or partial obstruction of extrahepatic bile ducts. The biliary tree is normal at birth and subsequently undergoes destruction that is thought to be immune-related or viral-induced. Infants may appear healthy at birth, but then present with jaundice within the first 2 months of life, along with dark urine and acholic (pale or clay-colored) stools due to excessive renal excretion of bilirubin and lack of intestinal bile, respectively. Physical examination may also reveal firm hepatomegaly due to inflammation. Laboratory findings, including elevated direct bilirubin and gamma-glutamyl transferase, are consistent with cholestasis. Liver biopsy is usually diagnostic and reveals intrahepatic bile duct proliferation, portal tract edema, and fibrosis. Urgent surgical intervention is required, as lack of intervention can lead to death (due to cirrhosis) usually within 2 years. (Choice B) Gilbert syndrome is an inherited, benign condition of reduced production of glucuronyl transferase, a hepatic enzyme responsible for glucuronidation (ie, conversion of bilirubin to its excretable form). Patients are usually asymptomatic except at times of stress (eg, fasting, illness) during which mild, indirect hyperbilirubinemia and jaundice are present. (Choice C) Galactosemia (galactose-1-phosphate uridyl transferase [GALT] deficiency) is characterized by defective metabolism of galactose, a breakdown product of lactose that is then normally metabolized to glucose. Both direct and indirect bilirubin levels may be elevated. However, infants would present with vomiting, diarrhea, and lethargy during the first few days of life due to inability to digest breast milk or formula. (Choice D) Breast milk jaundice causes an indirect hyperbilirubinemia that peaks at age 2 weeks. The pathogenesis likely involves an enzyme, beta-glucuronidase, in breast milk that deconjugates bilirubin. This causes increased absorption and, therefore, increased enterohepatic circulation of bilirubin. Urine and stool appearance are unaffected. (Choice E) Hemolytic disease of the newborn can result from Rh incompatibility (eg, Rh-positive infant and Rh-negative mother) or ABO incompatibility (eg, A+ infant and O+ mother). Patients develop jaundice on the first day of life due to indirect hyperbilirubinemia, and a positive direct Coombs (antiglobulin) test confirms the presence of antibody-mediated hemolysis. Educational objective: Biliary atresia, or obstruction of extrahepatic bile ducts, presents with jaundice, dark urine, and acholic stools in the first 2 months of life due to conjugated hyperbilirubinemia. Biopsy reveals intrahepatic bile duct proliferation, portal tract edema, and fibrosis. __________ References: Biliary atresia. (http://www.ncbi.nlm.nih.gov/pubmed/19533128) Pathogenesis of biliary atresia: defining biology to understand clinical phenotypes. (http://www.ncbi.nlm.nih.gov/pubmed/26008129)

A 4-Week-Old Boy Is Brought to the Office for a Routine