Clustering of mutations in the biotin-binding region of holocarboxylase synthetase in biotin-responsive multiple carboxylase deficiency

Holocarboxylase synthetase (HCS) catalyses the biotinylation of the four biotin-dependent carboxylases found in humans. A deficiency in HCS results in biotin-responsive multiple carboxylase deficiency (MCD). We have identified six different point mutations in the HCS gene in nine patients with MCD. Two of the mutations are frequent among the MCD patients analyzed. Four of the mutations cluster in the putative biotin- binding domain as deduced from the corresponding Escherichia coli enzyme and consistent with an explanation for biotin-responsiveness based on altered affinity for biotin. The two others may define an additional domain involved in biotin-binding or biotin-mediated stabilization of the protein.      

PROLONGED USE OF ISOFLURANE IN A PATIENT WITH TETANUS

We describe a patient with tetanus, who received isofluranefor sedation to facilitate controlled mechanical ventilation.Isoflurane was administered for 34 days, resulting in a sustainedserum inorganic fluoride ion concentration in excess of 50 µmollitre_–1 and a peak serum inorganic fluoride ion concentrationof 87 µmol litre_–1. Although these concentrationsare potentially nephrotoxic, no toxicity was evident clinically.     

Food and food additives in severe atopic dermatitis

In this study the role of food additives, tyramine and acetylsalicylic acid, was investigated by double-blind placebo-controlled challenges (DBPCC) in 25 children with severe atopic dermatitis (AD). All children challenged with foods (n = 24), except one, showed one or more positive reactions to the DBPCC with foods. Positive reactions presented as different combinations of flares of skin symptoms, intestinal symptoms and respiratory symptoms. Seventeen children (70.8%) showed a positive challenge to egg, 12 to wheat (50%), eight to milk (33.3%) and eight to soya (33.3%). Six children underwent DBPCC with food additives, tyramine and acetylsalicylic acid. All were found to demonstrate positive skin and/or intestinal reactions to at least one of the food additives. Two children reacted to tartrazine, three to sodium benzoate, two to sodium glutamate, two to sodium metabisulfite, four to acetylsalicylic acid and one to tyramine. It is concluded that some foods, food additives, tyramine and acetylsalicylic acid, can cause positive DBPCC in children with severe AD.