What genetic disorder results from the inability to break down phenylalanine and causes severe brain damage?

Phenylketonuria (PKU) is a genetic disorder caused by a deficiency in the enzyme phenylalanine hydroxylase, which is essential for the metabolism of phenylalanine, an amino acid found in many protein-containing foods. When phenylalanine is not broken down due to the lack of this enzyme, it accumulates in the body, leading to toxic levels that can cause severe brain damage and developmental delays if left untreated. Early diagnosis through newborn screening and a strict low-phenylalanine diet can significantly reduce the risk of cognitive impairment and allow for normal development.

In contrast to PKU, Down syndrome is a chromosomal condition caused by an extra copy of chromosome 21, leading to a variety of developmental and intellectual challenges. Cystic fibrosis is a genetic disorder affecting the respiratory and digestive systems due to a mutation in the CFTR gene, which produces a protein that helps control the movement of salt and water in and out of cells. Huntington's disease is a neurodegenerative genetic disorder caused by a mutation in the HTT gene, leading to progressive motor dysfunction and cognitive decline. Each of these conditions is distinct from PKU, particularly in their mechanisms and the specific biochemical pathways involved.