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Disease definition

A rare disorder of phenylalanine and tyrosine metabolism characterized by the accumulation of homogentisic acid (HGA) and its oxidized product, benzoquinone acetic acid (BQA), in various tissues (e.g. cartilage, connective tissue) and body fluids (urine, sweat), causing urine to darken when exposed to air as well as grey-blue coloration of the sclera and ear helix (ochronosis), and a disabling joint disease involving both the axial and peripheral joints (ochronotic arthropathy).


Classification level: Disorder
  • Synonym(s):
    • Hereditary ochronosis
    • Homogentisic acid oxidase deficiency
  • Prevalence: 1-9 / 1 000 000
  • Inheritance: Autosomal recessive 
  • Age of onset: Adult, Infancy
  • ICD-10: E70.2
  • ICD-11: 5C50.10
  • OMIM: 203500
  • UMLS: C0002066
  • MeSH: D000474
  • GARD: 5775
  • MedDRA: 10001689

Detailed information

General public


Disease review articles

Clinical Outcome Assessment (COA)

  • Patient-Centered Outcome Measures (PCOMs)
  • English (2023) - PROQOLIDTM
ERN produced/endorsed by ERN(s)   FSMR produced/endorsed by FSMR(s)
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