1. Phenylketonuria (disorder of amino acid metabolism)

a) Biochemical defect: deficiency of phenylalanine hydroxylase, which converts phenylalanine to tyrosine; increased blood levels of phenylalanine and increased urinary excretion of phenylpyruvic acid.


b) Clinical expression: symptoms in infancy or early childhood; mental retardation, seizure and hyperactivity


c) Detection: practically all newborns are screened (Guthrie test-serum analysis).


d) Therapy: low phenylalanine diet supplemented with tyrosine.

e) Pathological Characteristics:




-hypomyelination; gliosis; microcephaly


-no lysosomal storage in neurons

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