Central precocious puberty in a 3 year-old girl with Phenylketonuria: a rare association?

[phenylketonuria]

Central precocious puberty (CPP ) and phenylketonuria (PKU ) are two rare conditions , the latter being the rarer . To date , only one case featuring both these conditions has been reported , and hyperphenylalaninemia was assumed triggering CPP .We present a 3 .2 years old girl referred with a 12 months history of breast and pubic hair development , and vaginal discharge . Hyperphenylalaninemia had been identified by newborn screening and PKU subsequently confirmed by plasma amino acid and genetic analysis . Early dietary control of plasma phenylalanine had been excellent afterwards , resulting in phenylalanine concentrations consistently within the recommended range . Clinical scenario , hormonal assessment and imaging were in keeping with true idiopathic central precocious puberty . Treatment with long lasting gonadotropin-releasing hormone analogue led to regression of secondary sexual characteristics .We describe for the first time CPP in a girl affected with PKU but with persistently well controlled blood phenylalanine concentrations . This finding is in contrast to a previous report which suggested persistently high phenylalaninemia levels as potential trigger for CPP in PKU patients . Our report , together with the lack of evidence in published cohort studies of children with PKU , strongly suggests this rare association is coincidental and independent of the presence of severe hyperphenylalaninemia .