What disease causes a mouse urine-like odor?

A mouse-like urine odor may be caused by phenylketonuria (PKU).

The presence of a mouse-like odor in the urine or on the body is a specific characteristic of phenylketonuria. PKU is an inherited metabolic disorder resulting from a deficiency of the enzyme phenylalanine hydroxylase in the phenylalanine metabolic pathway, which leads to impaired or abnormal metabolism of phenylalanine. As a result, large amounts of phenylpyruvic acid metabolites are excreted in the urine of affected infants.

Infants with PKU usually appear normal during the first few months after birth. Without treatment, however, they begin losing interest in their surroundings at 3–6 months of age. By age one, significant delays in intellectual development become apparent, accompanied by symptoms such as intellectual disability, blank facial expressions, irritability, anxiety, unusual behaviors, and seizures. Additionally, excess phenylalanine and its metabolites are excreted through sweat and urine, producing a distinctive musty odor resembling that of mouse urine. It is important to seek medical evaluation at a qualified hospital, where medication can help control disease progression.

In daily life, maintaining balanced nutrition is essential. Individuals should consume as much phenylalanine-free food as possible and pay special attention when selecting infant formula. Seek medical advice promptly if any symptoms occur.