A 6-month-old full-term boy is brought to the emergency department with lethargy and vomiting. He was born by uncomplicated spontaneous vaginal delivery and has been growing and developing normally. The patient was breastfed exclusively until 2 days ago when homemade pureed food was added to his diet. He has had no fever or diarrhea. His parents are healthy and he has had no sick contacts. Examination shows a pale, diaphoretic, and ill-appearing infant. Serum glucose is 30 mg/dL. Diagnostic testing confirms aldolase B deficiency. Which of the following should be removed from this patient's diet?

Question

A 6-month-old full-term boy is brought to the emergency department with lethargy and vomiting.  He was born by uncomplicated spontaneous vaginal delivery and has been growing and developing normally.  The patient was breastfed exclusively until 2 days ago when homemade pureed food was added to his diet.  He has had no fever or diarrhea.  His parents are healthy and he has had no sick contacts.  Examination shows a pale, diaphoretic, and ill-appearing infant.  Serum glucose is 30 mg/dL.  Diagnostic testing confirms aldolase B deficiency.  Which of the following should be removed from this patient's diet?

Quizplus · Accepted Answer

11ec160b_369c_ce2d_9249_0bd74c2769e6_MD0001_00 Carbohydrates are classified as monosaccharides, disaccharides, and polysaccharides. Disaccharides and polysaccharides must be broken down to their monosaccharide components for energy production and utilization. Aldolase B metabolizes fructose-1-phosphate, a product of fructose metabolism, to dihydroxyacetone phosphate (DHAP) and glyceraldehyde, which can then enter the glycolytic pathway. Aldolase B deficiency can result in fructose-1-phosphate accumulation; this toxic metabolite depletes intracellular phosphate and inhibits the activation of hepatic phosphorylase and gluconeogenesis. The resulting condition, hereditary fructose intolerance (eg, fructosemia), is an autosomal recessive disorder. Because gluconeogenesis is impaired, fructosemia typically presents with life-threatening hypoglycemia. Consequences of hypoglycemia include lethargy, sweating, vomiting, and dehydration. These symptoms manifest after intake of fructose or sucrose, such as from formula or fruit. Strict abstinence from dietary fructose and sucrose can result in dramatic recovery. (Choices A and D) Starch (similar to glycogen in mammals) is the major storage form of carbohydrates in plants and contains only glucose molecules. Starch consists of an unbranched portion composed of amylose and a branched portion called amylopectin. Patients with fructosemia have normal metabolism of glucose. (Choice B) Cellulose is a linear polysaccharide of glucose that is mainly present in the cell wall of plant cells. Cellulose is an insoluble, indigestible dietary fiber that is responsible for the bulk of fecal matter. (Choices C, E, and F) Breast milk contains the disaccharides lactose (composed of galactose and glucose) and maltose (composed of 2 glucose molecules). Patients with aldolase B deficiency can consume these disaccharides as their breakdown will not produce fructose. However, patients with galactosemia cannot metabolize galactose in breast milk or cow's milk-based formula. These patients typically present in the first few days of life with jaundice, vomiting, poor feeding, and hepatomegaly. Educational objective: Aldolase B deficiency, or hereditary fructose intolerance, leads to accumulation of the toxic metabolite fructose-1-phosphate. Patients have hypoglycemia and vomiting when fructose or sucrose is consumed. Treatment involves strict removal of both carbohydrates from the diet. __________ References: Inborn errors of carbohydrate metabolism. (http://www.ncbi.nlm.nih.gov/pubmed/20955963) The biochemical basis of hereditary fructose intolerance. (http://www.ncbi.nlm.nih.gov/pubmed/20162364)

A 6-Month-Old Full-Term Boy Is Brought to the Emergency Department