[Diagnosis of deficiency in cofactor of phenylalanine hydroxylase: a metabolic emergency].

We report on two cases of children suffering from biopterin synthetase deficiency. Both were treated with the same treatment schedule with biopterin and neurotransmitters: 6-hydroxytryptophan and dihydrophenylalanine (DOPA). The only difference between the two cases is the time of diagnosis and therefore of treatment. The child who was treated early has a normal neurologic development. The other one has been treated since he was 7 months old and is mentally deficient (DQ = 0.60). This older child also suffers from dystonia probably secondary to Levodopa treatment. The authors emphasize the uncertainty of these patient's evolution owing to complications of the disease itself or those due to prolonged treatment by neurotransmitters.