Alkaptonuria - Alkaptonuria is a rare inherited genetic disorder of phenylalanine and tyrosine metabolism.
https://en.wikipedia.org/wiki/Alkaptonuria
Alkaptonuria: MedlinePlus - Alkaptonuria is a rare condition in which a person's urine turns a dark brownish-black color when exposed to air.
https://medlineplus.gov/
The AKU Society - An information and support network for those people diagnosed with Alkaptonuria.
https://akusociety.org/
