Ochronosis
![Pathophysiology of alcaptonuria, which is due to the absence of functional homogentisate dioxygenase in the liver.](/Images/godic/202501/30/Pathophysiology_of_metabolic_disorders_of_phenylalanine_and_tyrosine3559.png")
Ochronosis is the syndrome caused by the accumulation of homogentisic acid in connective tissues. The phenomenon was first described by Rudolf Virchow in 1865. The condition was named after the yellowish (ocher-like) discoloration of the tissue seen on microscopic examination. However, macroscopically the affected tissues appear bluish grey because of a light scattering phenomenon known as the Tyndall effect. The condition is most often associated with alkaptonuria but can occur from exogenous administration of phenol complexes like hydroquinone.