Which disorder presents with mental retardation, fair skin, and congenital pyloric stenosis?

The disorder that presents with mental retardation, fair skin, and congenital pyloric stenosis is Phenylketonuria (PKU). PKU is an autosomal recessive metabolic disorder that results from a deficiency in the enzyme phenylalanine hydroxylase. This enzyme is responsible for converting phenylalanine, an amino acid found in many protein-containing foods, into tyrosine. When this conversion is impaired, phenylalanine accumulates in the body, leading to neurotoxicity which manifests as intellectual disability if not managed appropriately.

The association with fair skin is due to the low conversion of phenylalanine to tyrosine, which is also a precursor for melanin, the pigment responsible for skin and hair color. As a result, individuals with PKU often have lighter skin and hair compared to their unaffected counterparts.

Additionally, congenital pyloric stenosis can be observed in some cases. While it is not unique to PKU and can occur in other conditions, the occurrence of pyloric stenosis in conjunction with the other symptoms can indicate PKU in a clinical context.

In contrast, the other conditions listed have different associated clinical features that do not include the combination of mental retardation, fair skin, and pyl