Abnormalities in urinary pterin levels in Rett syndrome.

The pterins, neopterin and biopterin, occur naturally in body fluids including urine. Increased neopterin levels are associated with activation of the cellular immune system and reduced biopterins are essential for biosynthesis of the monoamine neurotransmitters. The present study measured urinary neopterin and biopterin by high-performance liquid chromatography in 40 subjects with Rett syndrome, eight of their healthy sisters and 29 female control volunteers (age range 2-54 years). The results confirm earlier preliminary findings that urinary neopterin levels are raised in a proportion of young girls with Rett syndrome but not in the older women. In contrast urinary biopterin levels are not different from controls in the youngest children but remain low while control values increase with age. These findings may indicate immune activation during the regression phase of Rett syndrome but also raise the possibility that an inherited fault in tetrahydrobiopterin metabolism increases the risk of developing the disorder.