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bullous pemphigoid

Monday 31 January 2005

Digital cases

- UI:630 - Bullous pemphigoid

Images

- Bullous pemphigoid - subepidermal split with eosinophils and linear IgG and C3 on DIF

- urticarial bullous pemphigoid

Etiology

- auto-antibodies targeting BPAG1, one of the components of the basement membrane zone of the skin.

Pathogeny

Bullous pemphigoid is caused by antibodies directed against proteins at the dermal-epidermal junction. There is linear zone deposition of immunoglobulin and complement at this site (recall that the pattern for lupus erythematosus is similar, but granular in character).

Auto-antibodies are directed against protein BPAG1 at the dermal-epidermal junction.

Immunofluorescence

There is linear zone deposition of immunoglobulin and complement at this site (recall that the pattern for lupus erythematosus is similar, but granular in character).

Ultrastructure

Ultrastructural studies have shown that circulating antibody reacts with antigen present in the basal cell-basement membrane attachment plaques (hemidesmosomes).

The actual blister develops at the level of a narrow clear zone (lamina lucida) of the epidermal basement membrane that separates the underlying lamina densa from the plasma membrane of the basal cells.

The antigens present at these sites have been named bullous pemphigoid antigens 1 and 2, and they are now recognized as normal constituents of the hemidesmosomes that bind basal cells at the dermoepidermal junction.

In bullous pemphigoid, it is likely that the generation of autoantibodies to these basement membrane components results in the fixation of complement and subsequent tissue injury at this site through locally recruited neutrophils and eosinophils.

Degranulating eosinophils are often associated with necrosis of basal keratinocytes possibly related to the liberation of major basic protein from the eosinophil granule.

References

- Moll R, Moll I. Epidermal adhesion molecules and basement membrane components as target structures of autoimmunity. Virchows Arch. 1998 Jun;432(6):487-504. PMID: 9672190

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