Breastfeeding experience in inborn errors of metabolism other than phenylketonuria.

Breastfeeding has been recommended for the dietary treatment of infants with phenylketonuria, but studies documenting clinical experience in other inborn errors of metabolism are very few. Seven infants diagnosed with methylmalonyl-CoA mutase deficiency (n=2), ornithine carbamoyltransferase deficiency (n=1), propionic acidaemia (n=1), isovaleric acidaemia (n=1), maple syrup urine disease (n=1) and glutaric acidemia type I (n=1) were tried with breastfeeding over two years. After the control of acute metabolic problems, an initial feeding period with a measured volume of expressed breast milk plus a special essential amino acid mixture was continued with breastfeeding on demand and with the addition of a special essential amino acid mixture. Two patients with methylmalonic acidaemia and one patient with glutaric acidaemia type I tolerated breastfeeding on demand very well, with good growth and metabolic control for periods of 18, 8 and 5 months, respectively. In the patient with propionic acidaemia, on-demand breastfeeding continued for 3 months but was terminated after two acute metabolic episodes. The patient with isovaleric acidaemia had insufficiency of breast milk and formula supplementation ended with breast milk cessation. In the patient with severe ornithine carbamoyltransferase deficiency, breastfeeding was stopped owing to poor metabolic control. The patient with maple syrup urine disease also experienced problems, both in metabolic control and in insufficiency of breast milk, resulting in termination of breastfeeding. Breastfeeding of infants with inborn errors of protein catabolism is feasible, but it needs close monitoring with attention to such clinical parameters as growth, development and biochemistry, including amino acids, organic acids and ammonia.

Seventeen novel mutations that cause profound biotinidase deficiency.

We report 17 novel mutations that cause profound biotinidase deficiency. Six of the mutations are due to deletions, whereas the remaining 11 mutations are missense mutations located throughout the gene and encode amino acids that are conserved in mammals. Our results increase the total number of different mutations that cause biotinidase deficiency to 79. These additional mutations will undoubtedly be helpful in identifying structure/function relationships once the three-dimensional structure of biotinidase is determined.

Novel mutations cause biotinidase deficiency in Turkish children.

Mutation analysis was performed on DNA from 31 Turkish children with profound biotinidase deficiency who were symptomatic or ascertained by newborn screening. The 98G:del7ins3 mutation is common in clinically ascertained children in both the United States and Turkish populations, but a unique common mutation, R79C, is found only in the Turkish children identified both clinically and by newborn screening. Another frequently occurring mutation, T532M, is only observed in the Turkish newborn screening group. There are four other less frequent novel mutations identified in the Turkish population. Interestingly, the Q456H and the A171T:D444H double mutation, which are the most common mutations found in the US newborn screening population and have not been observed in symptomatic children, do occur in clinically ascertained children in the Turkish population, although the double mutation may be associated with milder and/or later-onset symptoms.

Partial biotinidase deficiency is usually due to the D444H mutation in the biotinidase gene.

Newborn screening for biotinidase deficiency has identified children with profound biotinidase deficiency (<10% of mean normal serum activity) and those with partial biotinidase deficiency (10%-30% of mean normal serum activity). Children with partial biotinidase deficiency and who are not treated with biotin do not usually exhibit symptoms unless they are stressed (i.e., prolonged infection). We found that 18 of 19 randomly selected individuals with partial deficiency have the transversion missense mutation G1330>C, which substitutes a histidine for aspartic acid444 (D444H) in one allele of the biotinidase gene. We have previously estimated that the D444H mutation results in 48% of normal enzyme activity for that allele and occurs with an estimated frequency of 0.039 in the general population. The D444H mutation in biotinidase deficiency is similar to the Duarte variant in galactosemia. The D444H mutation in one allele in combination with a mutation for profound deficiency in the other allele is the common cause of partial biotinidase deficiency.