A urine turns black after standing,develops a cloudy white precipitate,and has a specific gravity of 1.010.
-Based on the information provided,the most likely cause of the black color in this specimen is:

Question

Quizplus · Accepted Answer

The presence of a cloudy white precipitate along with a black color of urine after standing is indicative of the presence of homogentisic acid, which is the main marker for alkaptonuria. Homogentisic acid oxidizes on exposure to air and turns black, also forming a whitish precipitate due to its insolubility. This condition is characterized by the inability of the body to break down certain amino acids, leading to the accumulation of homogentisic acid in the urine and causing a darkening of the urine color after exposure to air. Methemoglobin, methyldopa, and melanin are not associated with the black color and precipitate formation seen in this case.

A Urine Turns Black After Standing,develops a Cloudy White Precipitate,and