Explain what happens in alkaptonuria and why there is a problem and what is this problem

It occurs when your body can’t produce enough of an enzyme called homogentisic dioxygenase (HGD). This enzyme is used to break down a toxic substance called homogentisic acid. When you don’t produce enough HGD, homogentisic acid builds up in your body. People with alkaptonuria also have urine that turns dark brown or black when it’s exposed to air