What color is alkaptonuria urine?

Alkaptonuria is a rare metabolic disorder that affects the breakdown of certain amino acids in the body. One of the distinctive features of alkaptonuria is the presence of dark-colored urine. Typically, the urine of individuals with alkaptonuria turns dark brown or black when exposed to air. This discoloration occurs due to the accumulation of a substance called homogentisic acid, which is normally broken down by an enzyme that is deficient in people with alkaptonuria. As a result, the excess homogentisic acid is excreted in the urine, leading to the characteristic dark color.