Phenylketonuria is not a risk factor for gut mucosa inflammation: a preliminary observation

Phenylketonuria (PKU) is an inborn error of amino acid metabolism in which high phenylalanine (Phe) concentrations in the central nervous system adversely affect its development and functioning. In PKU high oxidative stress and inefficiency of free radical scavenging may lead to systemic chronic inflammation. We hypothesised that in PKU gut mucosa is chronically inflamed and that this leads to release of calprotectin from neutrophils and monocytes.

The aim of this study was to compare intestinal mucosa inflammation status, as measured using fecal calprotectin, in patients with PKU irrespective of compliance, and healthy controls.

Forty-four patients with classical PKU were included in the study (21 male, 23 female; aged 0-41 years; mean ± SEM: 16.5 ± 1.7 years). Forty-eight healthy subjects (HS) aged 9-68 years (29.4 ± 2.6 years) comprised the control group, of whom 21 were male and 27 female. Among PKU patients 25 had normal Phe blood concentrations and in 19 they were elevated. In all subjects calprotectin stool concentrations were assessed (PhiCal ELISA, Calpro, Lysaker, Norway).

Normal FC (fecal calprotectin) concentrations were found in 43 (97.7%) PKU patients and 46 (95.8%) HS. No correlation between dietary control of Phe blood concentrations and FC levels in PKU patients was found.

No detectable intestinal inflammation occurs in phenylketonuria. Lack of dietary control and elevated Phe levels do not seem to be risk factors for inflammation of the mucosa of the gut.