Megaloblastic Anaemia Complicating Dietary Treatment of Phenylketonuria in Infancy.

Nutritional deficiencies may complicate the treatment of phenylketonuria by 'synthetic' phenylalanine restricted diets. This danger is greatest in infancy when growth is rapid. We report the occurrence of megaloblastic anaemia of infancy due to folic acid deficiency, during the dietary treatment of a baby with phenylketonuria. Case Report Simon B. was born at home on July 16, 1960, the third child of healthy unrelated parents. The pregnancy and delivery at full term were uneventful and his birth weight was 7i lb. (3*4 kg.). His eldest brother is mentally retarded and at the age of 7 years was found to have phenylketonuria; this was confirmed by paper chromatography of blood and urine. He has been on a low phenylalanine diet since that time with some improvement in his behaviour, but at 10 years old he has an I.Q. of 60. The second child is a normal boy of 5 years. Chromatographic examination of the urine of the parents and the second boy showed no abnormality. Simon appeared to be making normal progress on artificial milk feeds of half cream (Cow and Gate) and weighed 8 lb. (3 6 kg.) at 13 days old. Routine Phenistix testing of his urine at home by the Health Visitor at this time gave a strongly positive result, and he was admitted to hospital for investigation and dietary treatment. He was a fair, blue-eyed baby of normal appearance. His urine Phenistix tests were consistently positive and urine and blood chromatograms gave good spots for phenylalanine. The serum phenylalanine level by a biochemical method was 37 mg./100 ml. (normal up to 3 mg.) The haemoglobin was 120% and the white blood cells numbered 15,800/c.mm. with normal differential count. His normal milk feeds were replaced by a phenylalanine-restricted diet from the age of 2 weeks. For the initial depletion period 'minafen' was used in a 1 in 8 dilution, 25 oz. daily (20-25 mg. phenylalanine and 770 calories per day) with an 'abidec' vitamin supplement of