Fasting plasma kynurenine concentrations were significantly elevated i
n a group of 7 patients (4 female) conforming to DSM-III-R of the Amer
ican Psychiatric Association (1987) criteria for Tourette syndrome, in
comparison with 10 healthy controls (7 female). Simultaneous normal p
lasma biopterin and neopterin concentrations indicated that this rise
was probably not a consequence of peripheral cellular immune mechanism
s.