In the conversion of phenylalanine to tyrosine, phenylalanine hydroxylase (PAH), amino acid disorder and tetrahydrobiopterin (BH4) coenzymes are required.
These two enzymes are mainly derived from their own genes. Mutations in gene expression resulting in changes in the relevant genes may render these two enzymes ineffective, resulting in a large accumulation of abnormal phenylalanine in the body.
2. Clinical manifestations
There is no obvious social phenomenon for our children at birth, but as Chinese parenting progresses, symptoms will appear at 3-6 months of age and become more pronounced by the age of 1 year.
(1) Nervous system
The main clinical symptoms are agitation, hyperactivity or lethargy, muscle weakness, and a significant lag in mental development.
Most of the EEG tests will show abnormalities. The neurological damage of BH4 deficiency is much earlier and more severe. In addition to the similar symptoms mentioned above, children will die in early childhood if left untreated.
(2) Physical appearance
In children with BH4 deficiency, due to insufficient melanin synthesis, the infant will have lighter hair, skin and iris color after a few months of life. The skin will also become dry and the likelihood of eczema will increase.
Since phenylalanine and its intermediate target products in the process of metabolism are excreted in urine and sweat, this requires the presence of a rat urine odor.