Accumulation of homogentisic acid causes which of the tissue changes?

Ochronosis is the bluish black discoloration of ceain tissues, such as the ear cailage and the ocular tissue, seen with alkaptonuria. Alkaptonuria is a rare autosomal recessive metabolic disorder caused by deficiency of homogentisic acid oxidase. This deficiency results in accumulation and deposition of homogentisic acid (HGA) in cailage, causing the characteristic diffuse bluish black pigmentation. These affected connective tissue become weak and brittle with time, leading to chronic inflammation, degeneration, and osteoahritis. Ref: Textbook of Ohopaedics and Trauma By GS Kulkarni, 2009, Page 197; Clinical Paediatric Dermatology By Thappa, 2009, Page 156; Differential Diagnosis in Internal Medicine: From Symptom to Diagnosis, 2007, Page 347