[Relationship between the severity of brain damage in phenylketonuria and the degree of hyperphenylalaninemia]. / Zavisimost' tiazhesti porazheniia mozga pri fenilketonurii ot stepeni giperfenilalaninemii.

The frequency of the various degrees of the intellectual defect and convulsive syndrome was studied in 473 patients with phenylketonuria divided into four groups as regards the phenylalanine blood level, that was 150 to 199 mg/l in group I, 200 to 299 mg/l in group II, 300 to 399 mg/l in group III, and 400 mg/l and higher in group IV. A substantial increase of the number of patients with grave mental derangement and epileptic seizures was noted in groups II and IV: this shows that the risk of the grave mental affection is the greater the higher the phenylalanine serum level. An increased number of patients with a slight intellectual derangement in group I (43.2%) was noted, while in all other groups, the frequency of the mild course of the disease remained stable (about 7.5%). Possibility of existence of several pathogenic thresholds of hyperphenylalaninemia, as well as possible mechanisms of brain protection are discussed.