Epidermolysis Bullosa Acquisita
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Direct answer
Epidermolysis bullosa acquisita is an acquired subepidermal blistering disease caused by IgG autoantibodies against type VII collagen, the main component of anchoring fibrils. It produces mechanobullous blisters on trauma-prone sites such as the knuckles, elbows, knees, hands and feet, healing with milia and scarring. Direct immunofluorescence shows linear IgG at the basement membrane zone, often in a U-serrated pattern, and its association with inflammatory bowel disease is well recognised.
What you must remember
- Antigen: type VII collagen, the anchoring fibril protein at the dermal-epidermal junction, which is the target of IgG.
- Level of split: blisters form below the lamina densa, unlike the lamina lucida split of bullous pemphigoid.
- Morphology: tense blisters and erosions on friction sites, healing with milia, atrophic scarring and nail dystrophy.
- Mucosa: oral, oesophageal and ocular mucosa may be involved, sometimes with scarring.
- Histology: a subepidermal split with a neutrophil-rich infiltrate, although the picture can vary.
- Immunofluorescence: linear IgG and C3 at the basement membrane zone, sometimes described as U-serrated.
- Salt-split skin: IgG binds the dermal side of the split, which separates it from bullous pemphigoid.
- Associations: inflammatory bowel disease, especially Crohn disease, is well recognised, and other autoimmune conditions have been described.
A diagnostic route from blisters to bowel history
Fragile blisters on the hands that heal with milia and scarring, with no obvious trigger, point towards an acquired disorder. The steps below show how the diagnosis is confirmed and why the bowel history matters.
- Biopsy for histology. A biopsy of an early blister shows a subepidermal split, often with a neutrophil-rich infiltrate, which narrows the field to subepidermal blistering diseases.
- Confirm with direct IF. Linear IgG and C3 at the basement membrane zone confirm an autoimmune subepidermal disease.
- Use salt-split skin. Incubating skin in salt solution separates the dermis from the epidermis, and IgG binding to the dermal side points to EBA rather than bullous pemphigoid.
- Test for antibodies. Indirect IF on salt-split skin or an ELISA for anti-type VII collagen antibodies supports the diagnosis.
- Screen for associations. Ask about bowel symptoms and examine for other autoimmune disease, referring for gastroenterology review when inflammatory bowel disease is suspected.
- Treat in steps. Start with mild therapy such as dapsone or colchicine, reserve immunosuppressants and IVIG for severe disease, and protect the skin from trauma.
Where candidates lose marks
Examiners test whether candidates can separate this disease from the commoner bullous pemphigoid and recognise its systemic links.
- Trap: diagnosing bullous pemphigoid in an adult with trauma-induced blisters and milia Correct: this disease splits below the lamina densa, and its IgG binds the dermal side of salt-split skin, unlike pemphigoid.
- Trap: treating the blisters without asking about bowel symptoms Correct: inflammatory bowel disease is well recognised in this disease, so a gastrointestinal history is part of the work-up.
- Trap: expecting topical steroids alone to control chronic disease Correct: the disease is often refractory, so systemic therapy is frequently needed.
Frequently asked questions
Which antigen is targeted in epidermolysis bullosa acquisita?
Type VII collagen, the main component of anchoring fibrils, is the target of IgG autoantibodies in epidermolysis bullosa acquisita. Antibodies against this antigen weaken the dermal-epidermal junction and cause mechanobullous blisters.
What salt-split skin finding distinguishes epidermolysis bullosa acquisita from bullous pemphigoid?
In epidermolysis bullosa acquisita, IgG binds the dermal side of salt-split skin, whereas bullous pemphigoid antibodies bind the epidermal side. This finding helps separate the two subepidermal diseases on immunofluorescence.
Which conditions are associated with epidermolysis bullosa acquisita?
Inflammatory bowel disease, particularly Crohn disease, is well recognised in epidermolysis bullosa acquisita, and other autoimmune conditions have also been described. Screening for bowel symptoms is therefore part of the work-up.
Why does epidermolysis bullosa acquisita heal with milia and scarring?
Epidermolysis bullosa acquisita blisters form below the lamina densa, so healing involves the dermis and leads to milia and atrophic scars. Repeated blistering over trauma-prone sites also contributes to nail dystrophy.
Which drugs are used first for mild epidermolysis bullosa acquisita?
Dapsone and colchicine are commonly used first for mild epidermolysis bullosa acquisita, while immunosuppressants and intravenous immunoglobulin are reserved for severe or refractory cases. Dapsone requires haematological monitoring during treatment.