Laboratory investigations - autoimmune blistering skin or mucous membrane disease investigations, such as BP180 / 320 and Desmoglein 1 and 3

Overview

Serological and tissue-based testing for autoimmune blistering diseases - antibodies target specific structural proteins that maintain skin/mucosal integrity, and the target determines where in the skin blistering occurs
Bullous pemphigoid is the most common autoimmune blistering disease overall, typically affecting older adults

BP180 and BP230 - hemidesmosomal proteins anchoring the epidermis to the basement membrane - targeted in bullous pemphigoid; antibody binding here causes subepidermal blistering (tense bullae, basement membrane split)
Desmoglein 1 and 3 - desmosomal proteins holding keratinocytes to each other - targeted in pemphigus vulgaris/foliaceus; antibody binding causes intraepidermal blistering (flaccid bullae, acantholysis, positive Nikolsky sign)

Direct immunofluorescence of perilesional skin (linear IgG/C3 at the basement membrane for pemphigoid; intercellular "chicken-wire" IgG for pemphigus) plus serum ELISA/indirect immunofluorescence for circulating BP180/BP230 or desmoglein antibodies
Antibody titre correlates with disease activity in both conditions - useful for monitoring treatment response, unlike some other autoantibodies

High-potency topical or systemic corticosteroids are first-line for both; rituximab is increasingly used, particularly for pemphigus vulgaris given strong trial evidence
Pemphigus is generally more severe/higher-risk (mucosal involvement, fluid/electrolyte loss from widespread erosion) than bullous pemphigoid

Bullous pemphigoid, pemphigus vulgaris, dermatitis herpetiformis (coeliac-associated, granular IgA pattern), mucous membrane pemphigoid

Pemphigus vulgaris was historically associated with significant mortality before corticosteroids/immunosuppression; bullous pemphigoid, while less acutely dangerous, carries significant morbidity/mortality in the frail elderly population it typically affects

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