Cyst(e)ine Dependency Presenting with Growth Failure and Steatorrhea

Abstract

Initial study of a first-born male Caucasian child with classical celiac syndrome failed to reveal the cause of his growth failure: birth wt. 3.0 kg, age 12 weeks 3.3 kg. At age 16 weeks the child was admitted to hospital with an acute bout of diarrhea and dehydration. On fat-free intake, steatorrhea disappeared but hyperphagia and watery diarrhea with sugar-free stools persisted. Weight gain was less than normal for age. Following oral feeding of Amigen with glucose, alopecia occurred, and blood levels of methionine, ½ cystine, and taurine were > 115, <1.5, and 3.0 μM/dl respectively. Homocysting in blood and urine, and cystathionine in blood, were undetectable by ion exchange chromatography. Cystathionine was excreted in urine at less than 15 mg daily, dietary methionine averaging 6.5 μM daily. These findings suggested a block in the conversion of methionine to homocysteine.The essential nature of cystine for growth was documented in a series of feeding experiments. Three basic diets were used, providing the percentage distribution of calories as shown in the table. Caloric intake averaged 150 cal/kg/d. Weight gain was calculated from the average weight of the day before, day of, and day after a diet change. Diet were fed at least 6 days without significant change.Catch-up growth in body length and head circumference has occurred with dietary supplementation. Mental development seems normal but physical weakness persists.