PLASMA TOTAL ODD-CHAIN FATTY-ACIDS IN THE MONITORING OF DISORDERS OF PROPIONATE, METHYLMALONATE AND BIOTIN METABOLISM

Total plasma odd-numbered long-chain fatty acids were analysed in pati ents with methylmalonic acidaemia (vitamin B-12-responsive and unrespo nsive), combined methylmalonic acidaemia/homocystinuria (CblC), propio nic acidaemia (both neonatal-onset and late-onset), biotinidase defici ency and holocarboxylase synthase deficiency, as well as in hospital c ontrols. Total odd-numbered long-chain fatty acids (C-15:0, C-17:1 and C-17:0) were expressed as a percentage of total C-12-C-20 fatty acids . Control values were 0.72% +/- 0.31% (n = 12). Normalization of the p ercentage of odd-chain fatty acids occurred in all vitamin-responsive patients, following the institution of vitamin treatment. In general t he neonatal-onset propionic acidaemia and B-12-unresponsive methylmalo nic acidaemia patients had the highest plasma odd-chain fatty acid con centrations, which correlated with the clinical condition but not with the urinary excretion of methylcitrate or methylmalonate. Plasma odd- chain fatty acid concentrations and methylmalonate excretions in CblC patients reacted very well to vitamin B-12 treatment, but with no clin ical response. Measurement of plasma odd-chain fatty acids is of no va lue for the monitoring of defects of biotin metabolism.