Ochronosis (or alkaptonuria) refers to the bluish black discoloration of certain tissues, such as the ear cartilage and the ocular tissue, seen with alkaptonuria due to to excessive build up of homogentisic acid (HGA) which binds to collagen in connective tissue and making it weak and brittle with time, leading to chronic inflammation, degeneration, and osteoarthrosis (progressive arthropathy).