Abstract
Cerebrospinal fluid aminoacid analysis in a girl with severe psychomotor retardation,
hypotonia, hyperreflexia and growth acceleration showed highly increased levels of
free γ-aminobutyric acid (4.8 µmol/l; range in twenty controls 0.04-0.12, median 0.08),
homocarnosine, a dipeptide of γ-aminobutyric acid and histidine (23.4 µmol/l; control
range 4.0-8.7, median 7.6) and of β-alanine, an alternative substrate for γ-aminobutyric
acid-transaminase (0.48 µmol/l; control range 0.02-0.06, median 0.05). Liver γ-aminobutyric
acid-transaminase activity was deficient (0.07 µmol/mg protein h; range in ten controls
0.31-0.69, median 0.38). Fasting plasma growth hormone levels were increased (7.9-38.4
ng/ml; nl < 5). Brain evoked responses were suggestive of leukodystrophy. A brother
of this patient, showing a similar clinical picture, had died at one year. Postmortem
examination of his brain showed leukodystrophy of the type seen in amino acidopathies
such as phenylketonuria. This appears to be the first report of γ-aminobutyric acid-transaminase
deficiency.
Key words
β-alanine - GABA-transaminase deficiency - Gigantism - Homocarnosine - Leukodystrophy
