Granuloma Annulare (Visual Aid2)


S9C22VA2-1: This is a repeat of the drawing depicting connective tissue activation with particular emphasis on the temporal sequence as encountered in the evolution of a lesion of a palisaded granuloma. The vector of time is directed from left to right. On the left, cells are brown, collagen bundles are red, elastic fibers are yellow, and the interstitial matrix is blue. The initial response is an increased prominence of mucinous matrix with a reduction in the size, and number of collagen bundles (and a corresponding increase in the expanse of mucinous matrix among the collagen bundles; the collagen bundles are thinner and the spaces among the bundles are wider. Histiocytes have a role in the reduction in the size of collagen bundles and in the prominence of the mucinous matrix. At the full expression of this alteration, the affected area is relatively free of collagenous components and histiocytes form palisades at the margins of the mucinous zones. The elastica is more resistant than collagen bundles to the local increase in enzymes; they persist in the mucinous zones longer than do collagen bundles. Once the inciting agent has been digested in the enzyme-rich mucinous defect, the metabolism of dermal fibrocytes reverts to a fibroblastic phase and collagen bundles are reconstituted in the area of the defect. In granuloma annulare, a relatively normal interwoven pattern of coarsened collagen bundles mark the site of repair. In necrobiosis lipoidica, the reaction is marked by less mucin in the mucinous phase, and by a reconstitution of collagen bundles in “streaked” patterns (as illustrated on the right in this drawing).



S9C22VA2-2: In granuloma annulare, fibrolysis often affects collagenous components more rapidly, and to a greater extent, than it affects elastica. In this drawing of a lesion of actinic granuloma, the relationships between elastic fibers, histiocytes, and histiocytic giant cells are represented. Histiocytic cells are red. Elastic fibers are a pale lavender. The mucinous inter-celluar matrix is stringy and blue. There is an intimate relationship between histiocytes and elastic fibers. A giant cell has phagocytyzed elastic fibers. Often, such phagocytyzed elastic fibers take on a basophilic quality. As a lesion of this type progresses at its periphery, repair occurs centrally. The result of such a reaction in actinic granuloma is a trail of fibrotic dermis (characteristically, the upper 1/3 of the reticular dermis; specifically, the former domain of actinically damaged, elastotic connective tissue). The trail is devoid of elastotic material; the process is one of granulomatous elastolysis.

S9C22VA2-3: The activated (CD68 reactive) histiocyte, as seen in a palisaded granuloma, is rich in peripheral cell processes. In this drawing, a collagen bundle is represented at the top of the field (collagen fibrils are blue). Two elastic fibers (red with yellow sheaths) are represented to the left of the histiocyte. Cell processes extend into the collagen bundle at the top of the field. At the bottom of the field, the process is more advanced; the collagen fibrils are unbundled. Delicate red fibrils among the blue collagen fibrils are fibrin deposits. A palisaded granuloma is an inflammatory process; it is commonly associated with deposits of fibrin. A vasculitis may be associated with such a reaction but, clearly, the basic process involves collagenous tissue and is granulomatous; the process is a granulomatous collagenosis.

Up one tier if at tier 3, then up to respective parent CHAPTER; if at tier 2, then HOME

Next page sequential along a tier

Back a page spatial not temporal

Mauve bars provide access to other SECTIONS of this site

Green bars provide access to web sites

Beige bars provide access to additional photomicrographs and to parent CHAPTERS; they provide access to material not accessible with above cluster of Beige buttons