In the vast majority of patients, their ears will eventually begin to develop a blue-black colour. This is due to homogentisic acid (HGA) attaching itself to the cartilage present in ears. Like the spots in the eyes, this discolouration does not cause any pain or any other complications.
Patients may also experience black ear wax which is again caused by the accumulation of HGA.¹
An introduction to alkaptonuria and nitisinone