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Pemphigoid (tier 2)
The pemphigoids
are urticarial, vesicular, or bullous disorders, the initial insult being the formation of antigen-antibody complexes in the lamina lucida region of the basement membrane zone. The circulating antibody is anti-basement membrane zone in type and the antigen is BP antigen. The antibody generally is of the IgG class. On immunofluorescent preparations, the deposits are linear along the basement membrane zone with greatest intensity for IgG and/or C3.
Classically, lesions of pemphigoid are “cell-poor” at the dermal-epidermal interface. The defect is “sub-epidermal.” The basal cell layer of the roof of the bulla generally is
altered; a layer of ragged, pale acidophilic basal keratinocytes often is represented, or the layer of basal keratinocytes is not represented (presumably, having undergone lysis). In the latter pattern, the
keratinocytes along the lower margin of the roof of the bulla tend to be flattened, and spindle shaped (S6C16P10-1-4).
Some of the keratinocytes in the roof of a bullous lesion of pemphigoid may be clustered in the pattern of whorls; within the whorls, some of the keratinocytes tend to be necrotic
(the patterns resemble those of whorled transepidermal elimination as seen in the erythema multiforme complex); there may be cellular disarray in the roof of the bulla (the pattern of whorled transepidermal
elimination seems to be associated with processes which produce lysis and coagulation of basal cells). The epidermis forming the roof of the bullae may show hyperplasia, or may be thin. The keratin layer usually is
thin.
Along the floor of the defect, dermal papillae usually are preserved. With a reticulum, or PAS, stain, the basement membrane will be found along the floor, rather than attached to the
roof (S6C18P12-1). The papillary dermis often is edematous. Infiltrates of inflammatory cells are mostly
perivascular. Some examples are remarkably free of lymphoid infiltrates. Some show perivascular infiltrates of lymphocytes, histiocytes, and eosinophils. Some show plasma cells, as well as eosinophils, in the
infiltrates (S6C17P11-1-6). The angle formed at the margin, where an undetached epidermis forms an angle with the dermis,
usually is rather acute (S6C16P10-1 & 5). At the margin of a bulla, lymphocytes, and migratory histiocytes often are found
in linear arrays at the dermal-epidermal interface. Occasionally, neutrophils are found in the infiltrates at the dermal-epidermal interface. The subepidermal defects contain eosinophils, lymphocytes, histiocytes,
and a loose meshwork of fibrin.
Lesions of pemphigoid are sub-epidermal; as such, they are examples of “interface diseases.” The rounded, necrotic keratinocytes of apoptotic type, as seen in lesions of both erythema
multiforme and erythema multiforme-like disorders (S6C18P12-2 & 3), generally are not a prominent
feature of lesions of pemphigoid; scattered necrotic cells, and occasional clusters of such cells in patterns of whorled transepidermal elimination (erythema multiforme-like patterns) are occasional features in the
roof of lesions of pemphigoid.
Cell-poor, bullous lesions have been described in the setting of diabetic bullous dermopathy (S6C18P12-4). The histologic changes as documented in the literature have been variable.
Toonstra J: Bullosis diabeticorum: report of case and a review of the literature. J Am Acad Dermatol 1985;13: 799-805.
Cicatricial Pemphigoid
Lesions of cicatricial pemphigoid have a “fixed” quality; they tend to be localized and chronic (S6C19P13-1-7).
Although neutrophils occasionally may be a feature of the lesions of bullous pemphigoid, they are a regular feature of active lesions of cicatricial pemphigoid (S6C18P12-5-7).
Fleming T, Korman NJ: Cicatricial Pemphigoid. J Am Acad Dermatol 2000; 43: 571-91.
Chan LS, et al: The first international consensus on mucous membrane pemphigoid. Arch Dermatol 2002;138: 370-79.
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