The presence of homogentisic acid in urine typically leads to which urine color change?

The presence of homogentisic acid in urine typically leads to a brown or black color change due to the oxidation of this compound. Homogentisic acid is a product of the breakdown of the amino acids phenylalanine and tyrosine. In individuals with alkaptonuria, a genetic disorder that results in the accumulation of homogentisic acid, the compound becomes oxidized upon exposure to air, causing the urine to darken significantly.

This characteristic color change is an important diagnostic indicator in identifying conditions related to metabolic disorders and can be confirmatory for alkaptonuria. The darkening of the urine provides a visual clue that can signal further metabolic testing or evaluation by healthcare providers.