|
Lupus Erythematosus (tier 2)
Lichenoid dermatitides
are special variants in the general category of interface disorders. The lichenoid group is distinguished by morphologic markers of an immune-mediated reaction in which, by definition, the target cell is a keratinocyte. The phenomena, that are associated with a cellular immune reaction, normally are tightly controlled; they are inconspicuous in normal skin. In disease, the processes initiated by cell-mediated immune events include lysis of target cells and alterations in the morphologic expressions of keratinization; individual, pathologic cellular events, are the distinctive, morphologic expressions. The process, affecting keratinocytes and leading to morphologic changes, currently is characterized as (pathologic) apoptosis.
Lichenoid reactions can be divided into cell-poor (S5C6VA1-1) and cell-rich variants. Graft vs host reaction might be cited as the prototype for the
cell-poor category (S5C7P1-1). Lesions of lupus erythematosus (LE) generally fall in the category of a cell-poor lichenoid reaction. In such a
characterization, attention is given to the density and the expanse of lymphohistiocytic infiltrates in the papillary dermis in the immediate vicinity of the dermal-epidermal (D-E) interface. There are exceptions,
some of which are to be found in the lichen planus-lupus erythematosus overlap category.
The cutaneous manifestations of lupus erythematosus
vary with the severity of the disease (with severity being a correlate of the degree of systemic involvement). In lesions of systemic LE, the cutaneous manifestations may be subtle. Basement membrane deposits may be minimal and the suppression of basal unit differentiation may not be complete (S5C7P1-2). In other examples of SLE, basal unit differentiation may be suppressed and liquefaction at the D-E interface may be prominent. In these examples, the epidermis tends to be thin. Hyaline membranous deposits at the D-E (dermal-epidermal) junction are not always prominent (S5C7P1-3).
At the D-E junction in lesions of lupus erythematosus, lymphocytes and histiocytes are loosely arranged in linear arrays. In some examples, nuclear debris (a product of karyorrhexis) is a feature of the reaction at
the D-E interface (S5C7P1-4, & S5C9P3-1). The histiocyte appears to be an
important mediator of the degenerative changes at the D-E junction. Liquefaction degeneration is a feature of the immune reaction at the D-E junction in lesions of LE (S5C9P3-3-4). Well-defined, lytic defects and collections of colloid bodies usually are not a feature (if they are a prominent feature, then the
possibility of the lupus erythematosus-lichen planus overlap syndrome should be considered in the differential diagnosis) (S5C9P3-2, & S5C10P4-6).
Camisa C, Neff JC, Olsen RG: Use of immunofluorescence in the lupus erythematosus/lichen planus overlap syndrome: an additional aid in diagnosis. J Am Acad Dermatol 1984;11: 1050-9.
A common feature of a lesion of LE is a straight interface at the D-E junction (S5C7P1-4). It might be argued that this straight interface is the result of an
erosion of the rete ridges by the lichenoid process. A more plausible explanation would be that the lichenoid reaction has a deleterious effect on the epidermis in regard to phenotypic expressions. In this
approach, the expression of a basal unit phenotype is suppressed. In its place, the epidermis is entirely committed to terminal differentiation (expressed in the cytologic and histologic features of the superficial
unit of the epidermis). In the face of a deficient store of regenerating cells (a function of the basal unit), few, new cells are contributed to what becomes a phenotypically restricted epidermis. As a consequence,
the epidermis may not show significant acanthosis. In systemic LE, the epidermis often is thin (atrophic).
In some examples, the patterns at the D-E interfac and in the epidermis have a erythema multiforme-like quality (S5C7P1-5-6). Lesions of LE with EM-like
patterns are characteristic of the subacute variant (S5C9P3-6-7, & S5C9aP3a-1-2).
Callen JP: Drug-induced cutaneous lupus erythematosus, a distinct syndrome that is frequently unrecognized. J Am Acad Dermatol 2001;45: 315-316.
In lesions of LE, the basement membrane filters out immunoglobulins (IgG and IgM) and complement (this probably is a normal phenomenon, but is expressed in the extreme in LE); fibrin also is deposited. These
components, in collecting at the basement membrane level, produce a band-like deposit of “hyalin” at the D-E interface. This deposit is distincitve; when well-developed it is a feature strongly favoring a diagnosis
of LE (S5C10P4-4-5). In SLE, the deposits may be minimal (S5C8P2-1). In DLE, they usually are
well-developed (S5C8P2-2-3). It is, however, difficult to accurately characterized the stage (or state of dissemination) of the disease by placing great
emphasis on the character of the basement membrane zone.
In a lesion of discoid LE (DLE), follicular changes often are a prominent feature. In contrast to the cell-poor patterns at the D-E interface, the perifollicular patterns usually are cell-rich. Perifollicular
infiltrates tend to be band-like; they often fill the widened perifollicular sheath and press upon the follicular epithelium to produce lichenoid patterns(S5C10P4-2).
Vessels in the upper portion of the dermis are ectatic; often perivascular deposits of hyalin are a prominent feature (S5C10P4-1 & 3).
Lesions of LE have a life history. With time, the inflammatory changes may diminish and the dermis will undergo sclerosis (S5C9P3-5). Such
lesions might be confused with LS&A or superficial morphea.
Guenther LC: Inherited disorders of complement. J Am Acad Dermatol 1983;9: 815-39.
|
