One of the autoimmune blistering skin conditions characterised by flaccid intra-epidermal blisters
Aetiology
The most common (80%) subtype of the pemphigus group (includes 4 blistering autoimmune diseases that affect the skin and mucous membranes)
Autoimmune
Sex incidence is equal
Usually presents in middle age (40-60)
Drug triggers have been noted (such as ACEi and penicillamine), and it may be associated with an underlying malignancy as a paraneoplastic phenomenon
Pathophysiology
Type II hypersensitivity - IgG4 antibodies against desmosomal proteins lead to loss of keratinocyte adhesion (acantholysis - lysis of intercellular adhesion sites) in the skin and mucous membranes
This causes superficial (intra-epidermal) blisters that are easily deroofed, erosions and mucosal ulcers
Clinical features
Symptoms
Produces fluid-filled, painful, fragile blisters
Blisters rupture to form shallow erosions
Common sites: scalp, face, axillae, groin, trunk
May affect mucosa e.g. mouth, resp. tract
Extensive mucosal involvement may be fatal
Signs
Blisters will be Nikolsky sign positive - blisters can be extended with gentle lateral pressure
