A 15-month-old boy is brought to the office by his parents for poor weight gain. The parents have also noticed frequent, large, foul-smelling stools. He was admitted to the hospital for a prolonged bout of bacterial pneumonia 6 months ago. Both parents are healthy and have no similar symptoms. The child was born at term at home. He is at the 20th percentile for length and 3rd percentile for weight. Vital signs are normal. On examination, the child appears thin and has a nontender, nondistended abdomen. Which of the following is most likely present in this patient?

Question

A 15-month-old boy is brought to the office by his parents for poor weight gain.  The parents have also noticed frequent, large, foul-smelling stools.  He was admitted to the hospital for a prolonged bout of bacterial pneumonia 6 months ago.  Both parents are healthy and have no similar symptoms.  The child was born at term at home.  He is at the 20th percentile for length and 3rd percentile for weight.  Vital signs are normal.  On examination, the child appears thin and has a nontender, nondistended abdomen.  Which of the following is most likely present in this patient?

Quizplus · Accepted Answer

11ec160b_3ada_024b_9249_e107b93050d8_MD0001_00 This patient with failure to thrive, steatorrhea, and a hospitalization for pneumonia most likely has cystic fibrosis (CF). CF is an autosomal recessive disorder in which a defective chloride channel causes the accumulation of thick, dehydrated secretions in multiple organs. In the pancreas, viscous mucus obstructs small ducts and acini, preventing digestive enzymes from reaching the intestinal lumen and leading to progressive pancreatic inflammation and fibrosis. This ultimately causes pancreatic insufficiency, which may be present at birth in patients with CF and typically progresses throughout childhood. Signs of fat and protein malabsorption due to pancreatic insufficiency include steatorrhea (bulky, foul-smelling stools), failure to thrive, and fat-soluble vitamin deficiencies (A, D, E, and K). Elastase is a pro-enzyme (ie, zymogen) produced by pancreatic acinar cells and activated by trypsin within the duodenal lumen. Because elastase production and secretion are decreased in patients with pancreatic insufficiency, fecal elastase levels are also decreased; the presence of low fecal elastase is an accurate and noninvasive method for diagnosing pancreatic insufficiency of any cause (eg, CF, chronic pancreatitis). (Choice A) Dietary absorption of calcium is decreased in CF in part due to vitamin D deficiency, which leads to both hypocalcemia and increased calcium fecal concentration. (Choice C) Calprotectin is a protein derived from neutrophils that is released into the stool of patients with inflammatory diarrhea (eg, ulcerative colitis, Crohn disease). Fecal calprotectin levels are not increased in CF. (Choice D) Like elastase, chymotrypsin is a pancreatic digestive enzyme whose fecal concentration would be decreased (not increased) in patients with pancreatic insufficiency. (Choice E) Bicarbonate is produced and secreted by the pancreas to neutralize gastric acid and raise duodenal pH. Because patients with pancreatic insufficiency have less bicarbonate secretion, duodenal pH will decrease. The low pH can inactivate digestive enzymes produced by the stomach and intestine, further impairing nutrient absorption. Educational objective: Pancreatic insufficiency is common in cystic fibrosis because thick, viscous secretions in the pancreas block digestive enzymes, leading to malabsorption (eg, steatorrhea, failure to thrive). The presence of low fecal elastase is an accurate and noninvasive method for diagnosing pancreatic insufficiency. __________ References: Pancreatic pathophysiology in cystic fibrosis. (http://www.ncbi.nlm.nih.gov/pubmed/26365583)

A 15-Month-Old Boy Is Brought to the Office by His