Editing Rheumatoid arthritis (section)

===Skin===
The [[rheumatoid nodule]], which is sometimes in the skin, is the most common non-joint feature and occurs in 30% of people who have RA.<ref name=Tur2013>{{cite journal | vauthors = Turesson C | title = Extra-articular rheumatoid arthritis | journal = Current Opinion in Rheumatology | volume = 25 | issue = 3 | pages = 360–366 | date = May 2013 | pmid = 23425964 | doi = 10.1097/bor.0b013e32835f693f | s2cid = 21462453 }}</ref> It is a type of inflammatory reaction known to pathologists as a "[[necrotizing]] [[granuloma]]". The [[initial]] pathologic process in nodule formation is unknown but may be essentially the same as the synovitis, since similar structural features occur in both. The nodule has a central area of [[fibrinoid necrosis]] that may be [[fissure (anatomy)|fissured]] and which corresponds to the [[fibrin]]-rich necrotic material found in and around an affected synovial space. Surrounding the necrosis is a layer of palisading [[macrophages]] and [[fibroblasts]], corresponding to the intimal layer in synovium and a cuff of [[connective tissue]] containing clusters of [[lymphocyte]]s and [[plasma cell]]s, corresponding to the subintimal zone in synovitis. The typical rheumatoid nodule may be a few millimetres to a few centimetres in diameter and is usually found over bony prominences, such as the [[olecranon|elbow]], the [[calcaneal tuberosity|heel]], the [[metacarpophalangeal joints|knuckles]], or other areas that sustain repeated mechanical stress. Nodules are associated with a positive RF ([[rheumatoid factor]]) [[titer]], ACPA, and severe erosive arthritis. Rarely, these can occur in internal organs or at diverse sites on the body.<ref>{{cite journal | vauthors = Ziff M | title = The rheumatoid nodule | journal = Arthritis and Rheumatism | volume = 33 | issue = 6 | pages = 761–767 | date = June 1990 | pmid = 2194460 | doi = 10.1002/art.1780330601 | doi-access = free }}</ref>

Several forms of [[vasculitis]] occur in RA, but are mostly seen with long-standing and untreated disease. The most common presentation is due to involvement of small- and medium-sized vessels. Rheumatoid vasculitis can thus commonly present with skin ulceration and vasculitic nerve infarction known as [[mononeuritis multiplex]].<ref>{{cite journal | vauthors = Genta MS, Genta RM, Gabay C | title = Systemic rheumatoid vasculitis: a review | journal = Seminars in Arthritis and Rheumatism | volume = 36 | issue = 2 | pages = 88–98 | date = October 2006 | pmid = 17023257 | doi = 10.1016/j.semarthrit.2006.04.006 }}</ref>

Other, rather rare, skin associated symptoms include [[pyoderma gangrenosum]], [[Sweet's syndrome]], drug reactions, [[erythema nodosum]], lobe [[panniculitis]], [[atrophy]] of finger skin, [[palmar erythema]], and skin fragility (often worsened by corticosteroid use).<ref>{{Cite web |last=Moriyama |first=Takahiro |title=Chronic Disease |url=https://www.immunotherapy-clinic-ikiru.com/chronic-disease/ |access-date=2024-05-09 |website=Immunotherapy cancer and chronic disease |language=en-US}}</ref>

[[Diffuse alopecia areata]] (Diffuse AA) occurs more commonly in people with rheumatoid arthritis.<ref name=":1" /> RA is also seen more often in those with relatives who have AA.<ref name=":1">{{cite book | vauthors = Khan P, Beigi M |s2cid=46954629 |date=2018|title=Alopecia Areata|doi=10.1007/978-3-319-72134-7|isbn=978-3-319-72133-0 }}</ref>