A 2-year-old boy who attends daycare is brought to the emergency department due to diarrhea, fatigue, and abdominal cramps. The parents also state that he has foul-smelling, frothy stools. The boy is admitted for rehydration and subsequently diagnosed with giardiasis, which is treated with metronidazole. He improves and is discharged home. One week after discharge, the boy is seen by the primary health care provider for recurrent symptoms of frothy, loose stools and abdominal bloating and cramping. Which of the following steps of this pathway is most likely impaired in this patient?

Question

A 2-year-old boy who attends daycare is brought to the emergency department due to diarrhea, fatigue, and abdominal cramps.  The parents also state that he has foul-smelling, frothy stools.  The boy is admitted for rehydration and subsequently diagnosed with giardiasis, which is treated with metronidazole.  He improves and is discharged home.  One week after discharge, the boy is seen by the primary health care provider for recurrent symptoms of frothy, loose stools and abdominal bloating and cramping.  Which of the following steps of this pathway is most likely impaired in this patient?

Quizplus · Accepted Answer

11ec160b_36d4_3239_9249_535f9cee8c19_MD0001_00 Lactose is a disaccharide present in milk and other dairy products that is normally hydrolyzed into glucose and galactose by lactase, a brush border enzyme concentrated in epithelial cells of the small intestine. Lactose intolerance is due to decreased or absent lactase. Malabsorbed lactose then enters the large intestine where it is fermented by bacteria, causing the clinical features of lactose intolerance: diarrhea, flatulence, and abdominal bloating and cramping. Lactose intolerance can be either primary or secondary. Primary lactose intolerance is due to a genetically regulated reduction of lactase production, and its incidence increases with age. Secondary or acquired lactose intolerance can be due to inflammation (eg, celiac disease) or infection (eg, giardiasis) of the small intestine, both of which cause cellular damage to the intestinal lining. The damaged cells slough off and are replaced by immature cells with low lactase concentrations, resulting in a decreased ability to convert lactose to galactose. Secondary lactose intolerance is common after giardial infections. (Choices A, B, and C) Galactose-1-phosphate uridyl transferase (GALT) deficiency causes the most severe and most common form of galactosemia. Symptoms occur within the first few days of life after initiation of breastfeeding or formula and include vomiting, jaundice, hepatomegaly, and lethargy. Excess galactose is converted to galactitol by aldose reductase, resulting in cataracts from excess galactitol deposition in the lens. Galactokinase deficiency is a less common type of galactosemia, causing cataract formation only. (Choice D) Lactose synthase converts UDP-galactose to lactose within the mammary glands during milk formation. Deficiency of this enzyme does not result in lactose malabsorption. Educational objective: Secondary lactase deficiency can occur after inflammatory (eg, celiac disease) or infectious (eg, giardiasis) processes damage the microvilli of the small intestines. Clinical presentation includes abdominal distension and cramping, flatulence, and diarrhea. __________ References: Lactose intolerance. (http://www.ncbi.nlm.nih.gov/pubmed/26715083) Lactose intolerance in infants, children, and adolescents. (http://www.ncbi.nlm.nih.gov/pubmed/16951027) Lactose malabsorption (http://www.ncbi.nlm.nih.gov/pubmed/21063860)

A 2-Year-Old Boy Who Attends Daycare Is Brought to the Emergency