![]() Phagosomes of macrophages contain cell fragments and intact PMN’s. Crystals are strikingly absent within PMN infiltrating the synovium or in synovial vessels. Inflammatory cells are seen as described under light microscopy. In experimental urate crystal synovitis crystal phagocytosis by lining cells has also been seen (13) (Fig. The type A macrophage related cells have large vacuoles with granular material and cell debris and occasional definite crystal outlines in phagolysosomes (8). 8) (8).Įlectron Microscopy - During acute gouty arthritis there is surface fibrin-like material and proliferation of lining cells with predominance of Type B and intermediate cells. Fibrin like material has been seen between some tophi and the joint space ( Fig. Many synovial tophi are very superficial and often rather thinly encapsulated with fibrous tissue. ![]() Acute inflammatory cells are strikingly absent around tophi. The cells surrounding the tophus crystalsare fibrocytes, macrophages, other mononuclear cells and some foreign body giant cells. Tophi may also occasionally calcify with deposition of hydroxyapatite. Immunoglobulins have also been localized to tophi (12) ( Fig. Lipid stains show most lipid at the margins (5). There is faint PAS staining and some metachromasia. The matrix material around the crystals has been shown to contain cholesterol and mucopolysaccharides (5). If crystals are dissolved out leaving only the amorphous purple stained matrix, the former sites of tophi, they could be confused with rheumatoid nodules (5) although clefts from which crystals have been dissolved can often be seen. The DeGalantha stain or Gomori Methenamine silver stainalso can be used to stain the crystals (11) ( Fig. Urate crystals can alsobe easily identified in frozen sections or acetone fixed tissue of stained sections examined with compensated polarized light. 5) but alcohol fixation preserves them intact. Crystals are dissolved out by formalin based fixatives (10) ( Fig. Tophi consist of monosodium urate, needle shaped, crystals arranged radially ( Fig. Tophi are also clearly present in asymptomatic joints between attacks (5). ![]() Tophi are commonly seen in synovium, for example being found in 3 of 10 needle synovial biopsies in acute gouty arthritis (8) and in 4 of 6 biopsies in another series (9). Foreign body type giant cells have been seen near the surface. PMN infiltration may be striking in one piece of synovium while an adjacent specimen may show mainly chronic inflammatory cells. Vessels are congested and PMN may be marginated in the lumens of venules. Diffuse and perivascular infiltration by PMN is seen (Fig.2), but in addition there are almost always also lymphocytes, macrophages and even clumps of plasma cells ( Fig. Synovial lining cells are proliferated in some areas (8). Light Microscopy – During acute gouty arthritis an exudate containing PMN and fibrin adheres to the synovial surface. There is still some uncertainty as to whether this surface depositioncan be early or whether tissue deposits are always first. A diffuse crust of urates over virtually the entire synovial and/or cartilage joint surface can also occasionally be seen. Most are in the tissue and are not removed by irrigation (4-7). Crystal containing tophi may be seen in the tips or stems of villi. Gross – Tophi as refractile white clumps embedded in the synovium can fairly often be seen on the synovium surface at either surgery or autopsy. Synovial Biopsy, Synovium, Synovial Fluid & Arthrocentesis Gout Photo/Slide Viewer
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