View source for Tophus

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| name            = Tophus (Harrison Syndrome)
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| image           = GoutTophiElbow.JPG
| caption         = A tophus on the elbow of a middle aged man with chronic gout
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A '''tophus''' (Latin: "stone", {{plural form}}: '''tophi''') is a deposit of [[monosodium urate crystals]], in people with longstanding high levels of [[uric acid]] (urate) in the blood, a condition known as [[hyperuricemia]]. Tophi are [[pathognomonic]] for the disease [[gout]]. Most people with tophi have had previous attacks of acute [[arthritis]], eventually leading to the formation of tophi. Chronic tophaceous gout is known as [[Harrison Syndrome]].<ref>{{cite journal | pmc=5434697 | year=2017 | last1=Mirgh | first1=S. P. | last2=Venkatesh | first2=M. P. | title=Lumps All over: A Case of Chronic Tophaceous Gout (Harrison Syndrome) | journal=Indian Journal of Nephrology | volume=27 | issue=3 | pages=239–240 | doi=10.4103/0971-4065.202842 | pmid=28553051 | doi-access=free }}</ref>
Tophi form in the [[joints]], [[cartilage]], [[bone]]s, and other places throughout the body. Sometimes, tophi break through the [[skin]] and appear as white or yellowish-white, chalky [[Nodule (dermatology)|nodules]]. Without treatment, tophi may develop on average about ten years after the onset of gout, although their first appearance can range from three to forty-two years. The development of gouty tophi can also limit joint function and cause bone destruction, leading to noticeable disabilities, especially when gout cannot successfully be treated.<ref name=Edwards>{{cite book|last=Edwards|first=N. Lawrence|title=Primer on the Rheumatic Diseases|date=2008|url=http://dx.doi.org/10.1007/978-0-387-68566-3_12|pages=241–262|chapter=Gout A. Clinical Features |place=New York, NY|publisher=Springer New York|doi=10.1007/978-0-387-68566-3_12 |isbn=978-0-387-35664-8|access-date=2021-07-28}}</ref> When uric acid levels and gout symptoms cannot be controlled with standard gout medicines that decrease the production of [[uric acid]] (e.g., [[allopurinol]], [[febuxostat]]) or increase uric acid [[Waste|elimination]] from the body through the kidneys (e.g., [[probenecid]]), this can be referred to as [[Refractory disease|refractory]] chronic gout (RCG).<ref>{{cite journal |last=Ali|first=S|author2=Lally, EV |title=Treatment failure gout |journal=Medicine and Health, Rhode Island|date=November 2009 |volume=92 |issue=11 |pages=369–71 |pmid=19999896}}</ref>  They are more apt to appear early in the course of the disease in people who are older.
Although less common, tophi can also form in the kidneys and nasal [[cartilage]].
==Pathophysiology==
It appears that monosodium urate crystals trigger a distinct physiological [[neutrophil extracellular traps|NETosis]] pathway that coats them in DNA. These coated crystals then persist in tissues as a [[foreign body reaction|foreign body granuloma]] constituting gouty tophus.<ref>{{Cite web|title=Pathophysiology of Gouty Tophi|url=https://www.the-rheumatologist.org/article/pathophysiology-gouty-tophi/|access-date=2021-07-28|website=The Rheumatologist|language=en-US}}</ref>
==Additional images==
<gallery>
File:Gross pathology of tophus.jpg|[[Gross pathology]] of a large tophus
Image:Gouty_tophus_-_intermed_mag.jpg|[[Micrograph]] of a gouty tophus
Image:Tophus in knee.jpg|A tophus being removed from inside a [[knee]] joint by [[Arthroscopy|arthroscopic surgery]]
image:2015.7.30 Uric Acid synovial Tophus 7.tif|Tophus of uric acid crystals from toe joint fluid (100x polarized light)
</gallery>
==See also==
* [[Chondrocalcinosis]] (pseudogout)
==References==
{{Reflist}}
== External links ==
{{Commons category|Tophus}}
{{Medical resources
|  DiseasesDB     = 29389
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|  ICD9           = {{ICD9|274.0}}
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[[Category:Gross pathology]]
[[Category:Rheumatology]]