Section: USMLE

48) A Guatemalan child with a history of meconium ileus is brought to a clinic because of a chronic cough. The mother notes a history of respiratory tract infections and bulky, foul-smelling stools. After assessment of the respiratory tract illness, the practitioner should also look for signs of

1. cystinuria
2. hypoglycemia
3. iron deficiency anemia
4. sphingomyelin accumulation
5. vitamin A deficiency

The child likely has cystic fibrosis. In this disorder, an abnormality of chloride channels causes all exocrine secretions to be more viscous than normal. Pancreatic secretion of digestive enzymes is often severely impaired, with consequent steatorrhea and deficiency of fat-soluble vitamins, including vitamin A.

Cystinuria is a relatively common disorder in which a defective transporter for dibasic amino acids (cystine, ornithine, lysine, arginine; COLA) leads to saturation of the urine with cystine, which is not very soluble in urine, and precipitates out to form stones.

Hypoglycemia is not a prominent feature of children with cystic fibrosis who are on a normal diet. Hyperglycemia may occur late in the course of the disease.

Iron deficiency anemia is not typically found in children with cystic fibrosis.

Sphingomyelin accumulation is generally associated with deficiency of sphingomyelinase, as seen in Niemann-Pick disease.