Mild variant of maple syrup urine disease

Maple syrup urine disease variant form: presentation with psychomotor retardation and CT scan abnormalities

A female infant with an intermediate variant of maple syrup urine disease is described. The patient had psychomotor retardation and high plasma levels of branched chain aminoacids. Leucine decarboxylation rate in leukocytes was diminished. Cranial computed tomography showed decreased density in the cerebral white matter. After starting dietary treatment the infant resumed her psychomotor development and the abnormal images previously seen on computed tomography disappeared.

Thiamine-responsive inborn errors of metabolism

Three different inherited disorders are known in which thiamine may exert a beneficial effect: maple syrup urine disease (MSUD), lactic acidaemia and the syndrome of megaloblastic anaemia with sensorineural deafness and diabetes mellitus. The amounts of thiamine which were used for long-term treatment varied from 20 to 2400 mg day-1. Additional treatment, such as the reduction of dietary branched chain amino acids in MSUD, could not be omitted in some cases. It has been shown that the vitamin improves the stability of the branched chain ketoacid decarboxylase, although some weeks may be needed to observe the in vivo effect of treatment. A prolonged trial with high doses of thiamine should always be given.

Effects of thiamine in a patient with a variant form of branched-chian ketoaciduria

A boy with the intermediate variant of branched-chain ketoaciduria was studied. Treatment with an amino acid mixture was discontinued at the age of 7.5 years. Reintroduction of normal protein-containing foods precipitated the biochemical abnormalities, characteristic of MSUD, which were relieved by 10 mg thiamine/day. Adaptation to this regiment developed and thiamine intake was increased to 100 mg/day, later to 1 000 mg/day. The patient developed well and had no attacks of ketoacidosis. 1-14C-leucine degradation in intact fibroblasts was 15% of controls and did not increase upon addition of thiamine to the incubation medium.