Accumulation of homogentisic acid causes the following clinical condition:

Ochronosis is the bluish black discoloration of ceain tissues, such as the ear cailage and the ocular tissue, seen with alkaptonuria, a metabolic disorder. Exogenous ochronosis, in which bluish black pigmentation of cailage is noted iatrogenically by exogenous agents, has been seen after exposure to noxious substances, including phenol, trinitrophenol, benzene, and hydroquinone.