Editing Alkaptonuria (section)

==Signs and symptoms==
[[File:Ochronosis, Intervertebral discs Calcification. ZB.jpg|thumb|Intervertebral discs calcification due to ochronosis]]
Patients with alkaptonuria are [[asymptomatic]] as children or young adults, but their urine may turn brown or even inky black if collected and left exposed to open air.<ref name=Ranganath>{{cite journal |vauthors=Ranganath LR, Jarvis JC, Gallagher JA |title=Recent advances in management of alkaptonuria (invited review; best practice article) |journal=J. Clin. Pathol. |volume=66 |issue=5 |pages=367–73 |date=May 2013  |pmid=23486607 |doi=10.1136/jclinpath-2012-200877|s2cid=24860734 }}</ref> Pigmentation may be noted in the cartilage of the ear and other cartilage,<ref name=Ranganath/><ref name=Speeckaert>{{cite journal |vauthors=Speeckaert R, Van Gele M, Speeckaert MM, Lambert J, van Geel N |title=The biology of hyperpigmentation syndromes |journal=Pigment Cell Melanoma Res |volume=27 |issue=4 |pages=512–24 |date=July 2014  |pmid=24612852 |doi=10.1111/pcmr.12235 |doi-access=free }}</ref> and the [[sclera]] and [[corneal limbus]] of the eye.<ref>{{Cite journal|title = On the ocular findings in ochronosis: a systematic review of literature|journal = BMC Ophthalmology|date = 2014-01-30|issn = 1471-2415|pmc = 3915032|pmid = 24479547|pages = 12|volume = 14|issue = 1|doi = 10.1186/1471-2415-14-12|language = en|first1 = Moritz|last1 = Lindner|first2 = Thomas|last2 = Bertelmann | doi-access=free }}</ref>

After the age of 30, people begin to develop pain in the weight-bearing joints of the spine, hips, and knees. The pain can be severe to the point that interferes with activities of daily living and may affect the ability to work. Joint-replacement surgery (hip and shoulder) is often necessary at a relatively young age.<ref name=Ranganath/> In the longer term, the involvement of the spinal joints leads to reduced movement of the rib cage and can affect breathing.<ref name=Ranganath/> [[Bone mineral density]] may be affected, increasing the risk of [[bone fracture]]s, and rupture of tendons and muscles may occur.<ref name=Ranganath/>

[[Valvular heart disease]], mainly calcification and regurgitation of the [[aortic valve|aortic]] and [[mitral valve]]s, may occur, and in severe and progressive cases, [[valve replacement]] may be necessary. [[Cardiac arrhythmia|Irregularities in the heart rhythm]] and [[heart failure]] affect a significant proportion of people with alkaptonuria (40% and 10%, respectively).<ref name=Ranganath/> Hearing loss affects 40% of people. Also, a propensity to developing [[kidney stone]]s exists, and eventually also [[gallstone]]s and stones in the [[prostate]] and [[salivary gland]]s ([[sialolithiasis]]) can occur.<ref name=Ranganath/>