A 15-year-old boy comes to the office for a follow-up appointment. Since early childhood, he has suffered from recurrent respiratory infections and chronic diarrhea. The patient has been hospitalized several times for parenteral antibiotic treatment. Current prescribed medications include pancreatic enzyme therapy and a number of dietary supplements. Physical examination shows decreased proprioception and hyporeflexia in the lower extremities. Laboratory findings are suggestive of mild hemolytic anemia. Which of the following conditions is the most likely cause of these findings?

Question

A 15-year-old boy comes to the office for a follow-up appointment.  Since early childhood, he has suffered from recurrent respiratory infections and chronic diarrhea.  The patient has been hospitalized several times for parenteral antibiotic treatment.  Current prescribed medications include pancreatic enzyme therapy and a number of dietary supplements.  Physical examination shows decreased proprioception and hyporeflexia in the lower extremities.  Laboratory findings are suggestive of mild hemolytic anemia.  Which of the following conditions is the most likely cause of these findings?

Quizplus · Accepted Answer

The combination of recurrent respiratory infections and diarrhea in a child or young adult is strongly suggestive of cystic fibrosis with secondary exocrine pancreatic insufficiency. Because pancreatic enzymes are necessary for the proper absorption of nutrients in the gut, fat malabsorption with deficiencies of the fat-soluble vitamins A, D, E, and K frequently occurs in patients with cystic fibrosis. Vitamin E primarily serves to protect fatty acids from oxidation; vitamin E deficiency predisposes cell membranes to oxidative injury. The cells that are most susceptible include neurons with long axons (due to large membrane surface area) and erythrocytes (due to high oxygen exposure). The most common clinical manifestations of vitamin E deficiency are neuromuscular disease (eg, skeletal myopathy, spinocerebellar ataxia, polyneuropathy) and hemolytic anemia. Involvement of the dorsal column in the spinal cord is associated with the loss of proprioception and vibratory sense. Spinocerebellar tract involvement causes ataxia, and peripheral nerve dysfunction results in hyporeflexia. (Choices A, B, and C) Thiamine (vitamin B₁), riboflavin (vitamin B₂), and niacin (vitamin B₃) are water-soluble vitamins and not affected by fat malabsorption. (Choice D) Vitamin A deficiency manifests with night blindness, dry eyes (xerophthalmia), and corneal softening (keratomalacia). (Choice E) Vitamin C overdose can cause nausea, abdominal pain, and diarrhea. Chronic intake of high doses of vitamin C may facilitate the development of calcium oxalate kidney stones. (Choice F) Vitamin D is essential for bone formation and mineralization. Deficiency of this vitamin presents as rickets in children and as osteomalacia in adults. (Choice H) Vitamin K is necessary for hepatic synthesis of clotting factors II, VII, IX, and X. Deficiency of this vitamin presents as an increased tendency to bleed. Educational objective: Vitamin E deficiency can occur in individuals with fat malabsorption. Deficiency of this fat-soluble vitamin is associated with increased susceptibility of the neuronal and erythrocyte membranes to oxidative stress. Clinical manifestations include ataxia, impaired proprioception and vibratory sensation, and hemolytic anemia. __________ References: Vitamin E supplementation in people with cystic fibrosis. (http://www.ncbi.nlm.nih.gov/pubmed/25489958)

A 15-Year-Old Boy Comes to the Office for a Follow-Up