Discussion of Ochronosis
- Ochronosis is the bluish black discoloration of certain tissues, such as the ear cartilage and the ocular tissue, seen with alkaptonuria, a metabolic disorder.
- Ochronosis was defined by Virchow who histologically described the connective tissue in alkaptonuria, given the cartilage's ochre (yellow) hue under the microscope.
- Alkaptonuria is a rare autosomal recessive metabolic disorder caused by deficiency of homogentisic acid oxidase, resulting in a defect in the biochemical pathway for the degradation of phenylalanine and tyrosine.
- These affected connective tissue become weak and brittle with time, leading to chronic inflammation, degeneration, and osteoarthritis.
- Prevalence of Alkaptonuria in the US is 1 case per 1 million population.
- Alkaptonuria is present at birth and is often diagnosed by discoloration of the diapers.
- Up to 25% of patients with alkaptonuria do not have the characteristic dark urine staining, many patients remain undiagnosed until adulthood.
 Imaging Findings for Ochronosis