A 4-year-old child is assessed by the nurse. The child has fair skin, musty odor from the urine, stunted growth, and intellectual disability. Based on these findings, the nurse suspects which of the following metabolic disorders?


• Phenylketonuria (PKU) is an autosomal recessive metabolic disorder. Phenylalanine is an amino acid normally present in the body. It is tested for at birth to determine whether a baby has the enzyme needed to change phenylalanine into tyrosine. Without that enzyme, phenylalanine levels build up in the body and cause brain damage, microcephaly, and cerebral impairment.

• In untreated children with PKU, the hallmark sign of the disease is an intellectual disability. Other characteristics include fair skin, abnormal gait and posture, stunted growth, and urine with a musty odor.

Incorrect options:

• Branched-chain ketoaciduria, or maple syrup urine disease, causes an inability to break down branched-chain amino acids, leading to a buildup of waste products.

• Celiac disease is an autoimmune disorder in which gluten triggers an inflammatory response in the digestive tract.

• Tay-Sachs disease involves an inability to break down phospholipids, causing lipid accumulation in the brain and a rapid deterioration of mental and physical abilities.

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