Antigens

Hemidesmosomal protein 180 kDa BPAg2. Placenta may be the source of antigens.

Pathophysiology:

Similar to bullous pemphigoid

Clinicopathological Correlation:

Similar to bullous pemphigoid (refer to the Clinicopathologic

Correlation table, under the section "Bullous Pemphigoid").

Classification Variants, Mutations, and Other:

■ There is a high association with HLA-B8 and DR3, DR4 haplotypes.

■ There is a higher incidence of other autoimmune diseases (Hashimoto's, Graves, pernicious anemia) in individuals with pemphigoid gestationis.

Clinical:

■ Mucous membrane pemphigoid is a chronic blistering and scarring disorder involving mucosa, typically of elderly patients. Oral involvement is seen in 80%, ocular in 70%, and skin involvement in 20%. The oropharynx and nasopharynx are most commonly involved.

■ Eroded mucosal lesions are seen early, scarring is seen later (Fig. 5A). Eye involvement leads to symblepheron, where the scarred conjunctivae fuse together (Fig. 5B).

■ Mucosal-submucosal separation with submucosal fibrosis (Figs. 5C and D)

■ Blisters are uncommon, more typically, denuded submu-cosa and a strip of epithelium are present because the blister roof is sloughed (Fig. 5D)

■ Like BP, smooth not ragged blister roof

■ Submucosal infiltrates of lymphocytes, histiocytes, plasma cells, eosinophils, and neutrophils (Figs. 5E and F)

■ Neutrophils predominate over eosinophils compared with bullous pemphigoid

Differential Diagnosis:

■ Bullous pemphigoid with mucosal involvement

Immunofluorescence:

■ DIF: linear IgG and/or IgA and C3 at the epidermal basement membrane zone (Fig. 5G)

■ IIF: low titer IgG and IgA antibodies that bind to the basement membrane zone

■ IIF-SSS: most patients have immunoreactants on the epidermal side of the salt-split skin (Fig. 5H); patients with antibodies to laminin have immunoreactants on the dermal side (base) of the salt-split skin.

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