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rheumatoid nodule

Etiology: 1) rheumatoid arthritis (seropositive) [6] - methotrexate may increase risk of rheumatoid nodules [6] 2) Caplan's syndrome Pathology: 1) subcutaneous nodules over extensor surfaces & juxta-articular regions in ~1/3 of patients with rheumatoid arthritis 2) they also occur in the lungs, heart, kidney & dura mater 3) they are a manifestation of active disease Microscopic pathology: 1) angiocentric structure forming around the nidus of agranulomatous arteritis 2) central area of fibrinoid necrosis encircled by palisading fibroblasts & mononuclear phagocytes 3) perivascular chronic inflammatory infiltrate 4) collagenous capsule Clinical manifestations: - firm, mobile, asymptomatic subcutaneous nodules found over extensor joints & juxta-articular regions - elbows, fingers, or forearms - occur in ~1/3 of patients with rheumotoid arthritis - may be asymptomatic or painful [4] * images [5] Laboratory: - occur almost exclusively in patients with rheumatoid factor Differential diagnosis: - gouty tophus - tendon xanthoma - fibroma - subcutaneous granuloma annulare - malignancy, including metastatic lesions [6] Complications: 1) breakdown of the skin over rheumatoid nodules 2) ulceration & infection 3) spread of infection to local bursae, bone or hematogenous spread to distant joints 4) accelerated nodulosis - treatment with methotrexate or azathioprine increases frequency of rheumatoid nodules & may lead to the occurrence of nodules at unusual places such as fingertip pads

Related

Caplan's syndrome rheumatoid arthritis (RA)

General

abnormal morphologic structure (malformation)

References

  1. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 776
  2. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 824
  3. Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17. American College of Physicians, Philadelphia 1998, 2012, 2015
  4. Garcia-Patos V. Rheumatoid nodule. Semin Cutan Med Surg 2007 Jun 5; 26:100 PMID: 17544962
  5. DermNet NZ. Rheumatoid arthritis (images) http://dermnetnz.org/immune/rheumatoid.html
  6. Seetharaman M (slide show with images) Rheumatoid Arthritis: In and Out of the Joint. Medscape. March 22, 2016 http://reference.medscape.com/features/slideshow/rheumatoid-arthritis