title: [Black urine or black sclera of the eyes? Consider alkaptonuria].
abstract: BACKGROUND
  Alkaptonuria is a rare metabolic disorder due to a defect in the gene for homogentisic acid oxidase. This results in an accumulation of homogentisic acid, which leads to the deposit of pigment in the connective tissue in the body. This causes problems and symptoms in various organ systems, such as early artropathy, dark-coloured urine, black sclerae, dark-coloured aortic valves and an increased risk of kidney stones and gall stones. Various specialists may see patients with this disease. The diagnosis is often missed.
  
  
  METHODS
  We describe a 69-year-old woman who underwent surgery due to joint problems, which showed up black cartilage. It turned out that for many years she had also had eye and heart problems. Not until later in life was she diagnosed with alkaptonuria.
  
  
  CONCLUSIONS
  There is no curative treatment for alkaptonuria at the moment. Early recognition of the disease can increase the quality of life. Preventative check-ups and guidance are also therefore necessary.
authors.affiliation: Groene Hart Ziekenhuis, afd. Orthopedie, Gouda.
authors.forename: Nanda P
authors.initials: NP
authors.lastname: Gubbels
authors.forename: Merijn  H
authors.initials: M
authors.lastname: Sijbrand
authors.forename: Ron
authors.initials: R
authors.lastname: Onstenk
mesh_terms: D000368:Aged; D000474:Alkaptonuria / Q000175:diagnosis*; D005260:Female; D006801:Humans; D012590:Sclera / Q000473:pathology*; D014556:Urine