Methylmalonic acidaemia and nonketotic hyperglycinaemia. Clinical and biochemical aspects.

The clinical and metabolic data of 2 cases of methylmalonic acidaemia with propionic acidaemia are reported together with those of 3 other patients with nonketotic hyperglycinaemia. Liver enzymatic studies showed decreased activity in vitro of the glycine cleavage enzyme in one patient with methylmalonic acidaemia as well as in 2 unrelated patients with nonketotic hyperglycinaemia, while the activity of the serine hydroxymethylase enzyme was normal. Hyperammonaemia was substantiated in one patient with methylmalonic acidaemia and also in one child with nonketotic hyperglycinaemia. The activity of the enzymes of the urea cycle, determined in the liver of this nonketotic child, was normal except for a decrease of the carbamyl phosphate synthetase enzyme to 15% of normal.