A study by Timperio et al. in 2022 hypothesized that the low levels of tyrosine and DOPA in the urine of children with autism are due to a deficiency of the enzyme phenylalanine hydroxylase, which leads to a destabilization of the tyrosine–phenylalanine balance, with the imbalance of the gut microbiome and aggravation of autism spectrum symptoms [23]. The gene discussed is PAH; the disease is autism.