|
LE (continued) (tier 2)
Mucinous changes (S5C19VA-1) in connective tissue might be characterized as a form of
connective tissue activation. In some examples of lesions of LE, the mucinous changes extend into the subcutaneous fat; such an extension of mucinosis into the subcutaneous fat may be a simple expansion of the
mucinous changes that are common in the dermis in lesions of LE (S5C18P12-1). Such lesions may not be associated with prominent epidermal
changes of LE (S5C18P12-2). As an alternate interpretation, subcutaneous mucinosis in the setting of LE may be an expression of an early
stage of lupus profundus (panniculitis). The degree of inflammation in such lesions is variable. For some examples, histiocytes are a prominent feature of the mucinous changes in the dermis (S5C18P12-3 & 4). There have been recent additions to the category of mucinosis (S5C19VA2-3).
GRAFT vs HOST REACTION
The graft vs host reaction might be characterized as prototypic of a cell-poor lichenoid reaction. Although there are questions as to the exact role of humoral processes, as opposed to cell-mediated processes
(including cytotoxic T-cells), the morphologic features are in keeping with a reaction between activated T-cells and native epithelial cells; the problems relate to incompatibilities between the T-cells and the
antigens of the host.
The morphologic changes in acute graft vs host reaction can be compared to the changes in the skin in systemic, or subacute LE. The reaction begins with vacuolar changes at the dermal-epidermal interface; it
progresses to include degeneration of individual keratinocytes of the basal unit (S5C18P12-5-8); the role of lymphocytes in the alterations
affecting keratinocytes is manifested by the presence of a lymphocyte and/or histiocyte in close proximity to a dying keratinocyte (satellite cell necrosis) (S5C18aP12a-1-5).
LUPUS PROFUNDUS
Lupus profundus affects the subcutaneous tissue with variable patterns at the D-E interface. It is commonly associated with changes in the lower 1/3 of the reticular dermis. The changes may be mucinous but, for many
example, the changes clearly are sclerodermoid in character. The interface between the reticular dermis and the subcutaneous tissue often is straight (a sclerodermoid quality). Perivascular lymphohistiocytic
infiltrates are prominent; characteristically, they contain a component of plasma cells (a sclerodermoid quality). Interstitial infiltrates of lymphocytes and histiocytes (lymphohistiocytic collagenosis) are common
(a sclerodermoid quality) (S5C20P13-1-5).
The variety of alterations in the subcutaneous fat in lupus profundus depend in part on the age of the process at the time of biopsy (its histologic stage). Early lesions tend to have a mucinous quality. In the
mucinous areas, zones of fibrinoid necrosis develop. For some examples, the zones of necrosis are large and extensive. In the process of repair, some of the necrotic tissue becomes hyalinized (S5C20P13-5). Large necrotic lesions may also show extensive calcification.
Muscular veins of the subcutaneous fat in a lesion of lupus profundus are both infiltrated, and surrounded by, lymphocytes and histiocytes. The infiltrates contain an admixture of plasma cells.
Prussick R, et al: Polymyositis: a manifestation of chronic graft-versus-host disease. J Am Acad Dermatol 1991;25: 560-2.
DERMATOMYOSITIS
Dermatomyositis is manifested in the skin in patterns which often include many of the features of lupus erythematosus, including common cell-poor lichenoid patterns and dermal mucinosis; characteristically, in
lesions showing epidermal changes, the patterns are those of a cell-poor lichenoid dermatitis (S5C20aP13a-1, & S5C20aP13a-3 & 4). The epidermis often is thin with a straight interface. Vacuolar changes are prominent at the D-E
interface in some examples. Basement membrane hyalinosis generally is not a prominent feature. Dermal mucinosis is common (S5C20aP13a-2-5);
it may be a feature in the absence of significant vacuolar changes at the D-E interface. The changes in the skeletal muscle include interstitial infiltrates of lymphocytes and histiocytes and degeneration of
skeletal muscle fibers (S5C20aP13a-6 & 7).
|
