Ochronosis is caused by

In Alkaptonuria there is defect in catabolism of Tyrosine and Phenylalanine Enzyme deficient-Homogentisate Dioxygenase Homogentisic acid is an intermediate in the catabolism of Tyrosine Deposition of black pigments (polymerization of Homogentisic acid occurring in body over years) in joints, cailage and collagenous tissue is known as Ochronosis. DEPOSITION OF BLACK PIGMENTS