CPPD is frequently asymptomatic. However, it may produce acute, subacute, or chronic arthritis that can be confused clinically with OA or RA. The joint involvement may last from several days to weeks and may be monoarticular or polyarticular; the knees, followed by the wrists, elbows, shoulders, and ankles, are most commonly affected. Ultimately, approximately 50% of affected individuals experience significant joint damage. Therapy is supportive. There is no known treatment that prevents or slows crystal formation.
Osteoarthritis(OA,degenerativejointdisease),themostcommondiseaseofjoints,isadegenerativeprocessofarticularcartilageinwhichmatrixbreakdownexceedssynthesis.Inflammationisminimalandtypicallysecondary.Localproductionofinflammatorycytokinesmaycontributetotheprogressionofjointdegeneration.
Rheumatoidarthritis(RA)isachronicautoimmuneinflammatorydiseasethataffectsmainlysmalljoints,butcan http://ebooksmedicine.net besystemic.RAiscausedbyacellularandhumoralimmuneresponseagainstself-antigens,particularlycitrullinatedproteins.TNFplaysacentralroleandantagonistsagainstTNFareofclinicalbenefit.
SeronegativespondyloarthropathiesareaheterogeneousgroupoflikelyautoimmunearthritidesthatpreferentiallyinvolvethesacroiliacandvertebraljointsandareassociatedwithHLA-B27.
Suppurativearthritisdescribesdirectinfectionofajointspacebybacterialorganisms.
LymediseaseisasystemicinfectionbyBorrelia burgdorferi,whichmanifests,inpart,asaninfectiousarthritis,possiblywithanautoimmunecomponentinchronicstages.
Goutandpseudogoutresultfrominflammatoryresponsestriggeredbyprecipitationofurateorcalciumpyrophosphate,respectively.
Fig.21.43Pseudogout.(A)Depositsarepresentincartilageandconsistofamorphousbasophilicmaterial.(B)Smearpreparationofcalciumpyrophos-phatecrystals.
Reactive tumorlike lesions, such as ganglions, synovial cysts, and osteochondral loose bodies, commonly involve joints and tendon sheaths. They usually result from trauma or degenerative processes and are much more common than neoplasms. Primary neoplasms are rare, usually benign, and tend to recapitulate the cells and tissue types (synovial membrane, fat, blood vessels, fibrous tissue, and cartilage) native to joints and related structures. Synovial sarcoma, although once thought to be related to or derived from the tissues of the joint, is now recognized as a sarcoma of uncertain origin and is discussed later with soft tissue tumors.
A ganglion is a small (1–1.5 cm) cyst that is almost always located near a joint capsule or tendon sheath. A common location is around the joints of the wrist, where it appears as a firm, fluctuant, pea-sized translucent nodule. It arises as a result of cystic or myxoid degeneration of connective tissue; hence the cyst wall lacks a cell lining. The lesion may be multilocular and enlarges through coalescence of adjacent areas of myxoid change. The fluid that fills the cyst is similar to synovial fluid; however, there is no communication with the joint space. Despite the name, the lesion is unrelated to ganglia of the nervous system.
Herniation of synovium through a joint capsule or massive enlargement of a bursa may produce a synovial cyst. A well-recognized example is the synovial cyst that forms in the popliteal space in the setting of RA or OA (Baker cyst). The synovial lining may be hyperplastic and contain inflammatory cells and fibrin.