Epidermolysis bullosa acquisita

Meet the patient

A 48-year-old man with known Crohn's disease develops tense blisters on the backs of his hands, elbows, and feet over two months, appearing wherever he knocks or grips. Old erosions heal with tiny white seed-like cysts and shiny scars, and his nails are thickening and distorting. A skin biopsy reports "subepidermal blister, linear IgG and C3 at the basement membrane — bullous pemphigoid."^[1][10]

Two questions decide his diagnosis and his entire treatment pathway, and they are the two that decide every blistering case: is the split superficial or deep? (the salt-split skin answers it) and does it scar? (the clinical history answers it). Hold those two questions and this disease, which hides so often behind the wrong label of "resistant pemphigoid", falls into view.^[1]

Why the deep split scars — type VII collagen and the anchoring fibril

EBA is the only common blistering disease whose autoimmune target sits below the lamina densa, and that single fact explains everything that follows. Type VII collagen, a 290 kDa homotrimer encoded by COL7A1, is the exclusive protein of the anchoring fibrils — curvilinear struts that project from the underside of the lamina densa into the papillary dermis, trap interstitial collagen, and rivet epidermis to stroma.^[6]

The autoimmune cascade runs in three steps, and each is the target of a therapy. IgG autoantibodies (IgG1 and IgG4) bind the amino-terminal NC1 domain of type VII collagen — the dominant epitope and the substrate of the commercial ELISA. Antibody binding activates complement, generating C5a, which recruits neutrophils. Degranulating neutrophils release elastase and matrix metalloproteinase-9, digesting the anchoring fibrils themselves.^[6]

The split therefore forms below the lamina densa — deeper than any other pemphigoid — which is why the roof shears off under trauma, why healing lays down scar and traps milia, and why the salt-split skin reads "floor". The antibody is pathogenic, not a bystander: active immunisation with type VII collagen reproduces the disease in animal models.^[6]

Etymology for viva gold: the name epidermolysis bullosa acquisita is deliberately diagnostic — acquisita, Latin for "acquired", sets this adult-onset autoimmune disease against the inherited (hereditaria) dystrophic EB caused by germline COL7A1 mutations. Same target, same scarring phenotype, opposite mechanism.^[2]

One antibody, four faces — the clinical variants

The same anti-type VII collagen antibody wears four masks, and recognising each is the whole diagnostic game because the inflammatory and mucosal forms are easily mistaken for commoner diseases.^[2][4]

^{[1] [4]}

The classic trap: a patient labelled "treatment-resistant bullous pemphigoid" is the single commonest presentation of EBA. The two share a subepidermal blister and linear IgG and C3 on direct immunofluorescence — and without a salt-split test the patient is sentenced to escalating, ineffective steroids. The rescue is the salt-split floor pattern plus an anti-type VII collagen ELISA.^[3][5]

The salt-split skin — the one test that wins the viva

This is the single most reproduced discriminator in blistering-disease exams, and it is anatomical, not arbitrary. Normal human skin is split through the lamina lucida by incubation in 1 mol/L sodium chloride. The artificial cleave places BP180 and BP230 (hemidesmosomes) on the roof and type VII collagen (anchoring fibrils) on the floor — so the patient's circulating antibody reveals its target by the side it lights up.^[5]

^{[1] [5]}

One-line discriminator beneath the table: floor and scarred and stubborn = EBA; roof and clean and steroid-responsive = BP.^[2]

What juniors forget: direct immunofluorescence can never diagnose EBA. Linear IgG and C3 along the basement membrane zone is identical to bullous pemphigoid and mucous membrane pemphigoid — DIF only establishes that the disease is a basement-membrane pemphigoid, then hands the decision to the salt-split test. The definitive ultrastructural localisation is immunoelectron microscopy showing deposits below the lamina densa — the historical gold standard written into the 2018 definite-EBA criteria.^[3][5]

The International Bullous Diseases Group 2018 — definite, probable, possible

Diagnosis is standardised by the IBDG 2018 consensus, and examiners expect the four pillars of "definite EBA" verbatim. Definite EBA requires all of: a non-inherited blistering disorder compatible with EBA; no evidence of an alternative diagnosis; direct immunofluorescence showing linear IgG, IgA, or C3 along the basement membrane zone; and immunolabelling localised to the floor of salt-split skin, OR immunoelectron microscopy showing deposits below the lamina densa, OR a positive anti-type VII collagen ELISA.^[3]

Probable EBA lacks one criterion; possible EBA lacks two. The 2018 consensus is the global reference that replaced the older, looser definitions — quote the four pillars, and you have the diagnostic half of the viva.^[3]

^[1]

The mimics — every subepidermal blister is a suspect

The differential of EBA is the entire family of subepidermal blistering diseases, and the discriminators are distribution, scarring, immunofluorescence — and the salt-split side. Before you commit to EBA, run the salt-split, the ELISA, and the porphyrins, because each mimic has a single test that parts it cleanly.^[5]

^{[2] [5]}

Two classical examination stems deserve a name because they recur. Pseudoporphyria (bullous dermatosis of haemodialysis) mimics both PCT and EBA on the dorsal hands — fragility, milia, scarring in sun-exposed skin — but has normal urine, plasma, and faecal porphyrins and normal immunofluorescence, separating it cleanly from both. It is usually drug-induced (NSAIDs, especially naproxen; furosemide) or arises on dialysis.^[2]

The classical mechanobullous variant is most often confused with porphyria cutanea tarda (dorsal hands, milia, scarring); the discriminator is sun-exposed distribution plus elevated porphyrins plus normal immunofluorescence in PCT. The mucous membrane variant is confused with mucous membrane pemphigoid — but EBA tends to have more skin involvement and a floor pattern on salt-split, whereas classical MMP reads roof.^[5]

The bedside round — find the variant, then find the Crohn's

Examination in suspected EBA has three jobs: decide the variant, screen the mucosa for scarring, and hunt for associated disease. Distribution first: extensor trauma-prone bullae point to the classical variant; widespread flexural bullae to the inflammatory variant; mucosal-dominant scarring to the mucous membrane variant.^[1]

Note the hallmarks at healed sites — milia and scarring are the cutaneous signature of EBA — and examine the nails (dystrophy, loss) and scalp (scarring alopecia). Then turn to the mucosa, which is where the morbidity hides: inspect the oral cavity for erosions and desquamative gingivitis, ask about dysphagia and hoarseness (oesophageal and laryngeal involvement), examine the conjunctivae for symblepharon, and inspect the anogenital mucosa.^[2]

Any ocular involvement mandates same-day ophthalmology referral — scarring progression to symblepharon and corneal blindness can be rapid and irreversible. In the history, screen hard for Crohn's (abdominal pain, diarrhoea, rectal bleeding, weight loss), lupus and rheumatoid arthritis, and a careful drug history — specifically penicillamine, captopril, and vancomycin.^[10][12]

Why Crohn's — and the drug triggers

The single strongest disease association is inflammatory bowel disease, above all Crohn's disease, and it is mechanistic, not coincidental. Both conditions share type VII collagen as an autoimmune target, and the colonic epithelium expresses type VII collagen at its basement membrane — a plausible bridge from mucosal inflammation to cutaneous autoimmunity. The blistering may precede, accompany, or follow the IBD, and must be treated independently.^[10]

^{[1] [12]}

The consultant confession: in any new adult blistering disease that scars, take the drug history before the biopsy result comes back. A patient on long-term penicillamine for Wilson disease may resolve completely on drug cessation plus a short steroid bridge, sparing them years of immunosuppression.^[12]

Management — the anti-neutrophil first, the steroid sparing second

EBA is notoriously steroid-resistant, and that resistance is the practical expression of a deep, mechanically loaded target and a sustained T-cell-driven antibody response. Treatment therefore combines anti-neutrophilic agents (colchicine, dapsone) with disease-modifying immunosuppression, escalating to rituximab and antibody removal in refractory disease.^[1][4]

^{[1] [2] [4] [14] [15]}

Colchicine and dapsone are the two anti-neutrophilic agents, used for mild disease; both appear in every published EBA treatment list. Dapsone is withheld until G6PD testing has excluded deficiency. The reason is mechanical: in G6PD-deficient red cells, dapsone's hydroxylamine metabolite causes haemolysis, methaemoglobinaemia, and agranulocytosis, so blood counts need close monitoring after the first dose.^[4][14]

Rituximab (anti-CD20) depletes the B cells that make the anti-type VII collagen antibodies. A 2024 systematic review of 31 studies, mostly in recalcitrant EBA, recorded clinical response in 92.7 percent and remission in 73.8 percent; relapse followed in 39.5 percent over a mean 23 months. Adverse events affected 28.2 percent, mostly mild, transient infusion reactions. The same authors' IVIG review found remission in 78.6 percent of EBA patients treated with IVIG.^[7][8]

^{[2] [4] [14] [15] [7] [8]}

Management by variant — match the drug to the face

Each variant has a preferred first move. The classical mechanobullous variant starts with an anti-neutrophilic agent, colchicine or dapsone, supplemented by a steroid-sparing agent when needed; corticosteroids have a limited role because the inflammation is modest. Corticosteroids and the immunomodulators are alternatives for mild forms of disease.^[1][4]

The inflammatory BP-like variant is managed much like bullous pemphigoid — corticosteroids for induction combined with a steroid-sparing agent — but is more refractory and escalates more often to rituximab. The mucous membrane (MMP-like) variant demands the most aggressive approach: early combination immunosuppression (corticosteroid plus cyclophosphamide or rituximab) to prevent irreversible ocular and airway scarring.^[4]

Childhood EBA typically presents with the inflammatory or mucosal phenotype; in the largest paediatric review, 40 cases, mucosal tissues were affected in 29. Treatment mostly consisted of a systemic corticosteroid combined with dapsone, and prognosis is favourable: 17 of 40 children achieved complete remission.^[9]

Drug-induced EBA (penicillamine, captopril, vancomycin) typically resolves on drug cessation with a short corticosteroid bridge — the drug history is the treatment, not the biopsy.^[12]

The preventable-harm list — do not miss the eye

The complications of EBA reflect both the disease and its treatment, and three of them are preventable if caught early. The mucosa is where EBA maims, and the ocular surface is where it blinds.^[2]

• Ocular scarring — symblepharon, synechiae, corneal opacity, blindness. Every patient with mucous membrane EBA needs routine ophthalmology surveillance; the window for preventing symblepharon is narrow and the damage is irreversible.
• Oesophageal strictures — dysphagia, weight loss, malnutrition. Refer early for endoscopic dilatation and nutritional support.
• Laryngeal stenosis — stridor, airway threat. Urgent ENT assessment; airway compromise is the rare true EBA emergency.

^[2]

The principal diagnostic pitfall is misdiagnosis as bullous pemphigoid — the patient is then exposed to escalating and ineffective corticosteroids while the true target sits untouched. The salt-split test and anti-type VII collagen ELISA are the safeguards. A second pitfall is missed ocular involvement: a patient may have minimal cutaneous disease but rapidly progressive conjunctival scarring, and the blindness is preventable only if the ophthalmology referral is early.^[5]

Prognosis, guidelines, and regional thresholds

EBA is a chronic, relapsing, often treatment-resistant disease that may persist for years or decades. The classical mechanobullous variant has the best skin prognosis but the most visible scarring; the inflammatory variant tends to relapse and remit; the mucous membrane variant has the worst prognosis, driven by irreversible ocular and airway damage. Mortality is significant and is largely attributable to complications of disease (sepsis, malnutrition, airway compromise) and toxicity of treatment.^[1]

Childhood EBA generally has a more favourable prognosis, often responding well to dapsone and entering remission within a few years. All patients need long-term dermatology follow-up; those with mucosal disease need parallel ophthalmology, gastroenterology, and ENT input.^[9]

The mantra, and the mnemonic

^[1]

The mantra: floor and scarred and stubborn — that is EBA; roof and clean and responsive — that is BP. Never label a pemphigoid treatment-resistant until the salt-split is done.^[1][3]

^[1]

Ward-round test

Stem 1 — A 72-year-old woman is labelled "bullous pemphigoid" but her blisters have not responded to three months of prednisolone. New bullae keep appearing on her dorsal hands and knees, and old erosions heal with milia and scarring. What is the likely truth, and which test confirms it?^[5]

AnswerShowHide

The likely truth is epidermolysis bullosa acquisita misdiagnosed as treatment-resistant BP — scarring and milia on trauma-prone extensor surfaces are the EBA signature. Direct immunofluorescence of a perilesional biopsy remains the diagnostic gold standard; indirect immunofluorescence on salt-split skin showing floor (dermal-side) binding separates EBA from BP and anti-p200 pemphigoid, and detection of antibodies against type VII collagen identifies the target antigen. Re-label the disease before escalating therapy.^[1][5][13]

Stem 2 — A 50-year-old man with Crohn's disease develops tense bullae on his dorsal hands that heal with scarring and milia. Direct immunofluorescence shows linear IgG and C3 at the basement membrane zone. Why the association, and what is the salt-split pattern?^[10]

AnswerShowHide

Both Crohn's disease and EBA share type VII collagen as an autoimmune target — the colonic epithelium expresses type VII collagen at its basement membrane, providing the mechanistic bridge. The salt-split pattern is FLOOR (dermal side), because type VII collagen sits below the lamina densa. Treat the blistering concurrently with the IBD; colchicine is a reasonable first move.^[1][10]

Stem 3 — A patient with the mucous membrane variant of EBA has minimal skin disease but is referred for "red eye". What is the preventable harm, and what do you do today?^[2]

AnswerShowHide

The preventable harm is irreversible ocular scarring — symblepharon, synechiae, corneal opacity, and blindness — which can progress within weeks. Act today with a same-day ophthalmology referral, topical lubricants and steroids, and division of forming synechiae; escalate the systemic immunosuppression to combination therapy (corticosteroid plus rituximab or cyclophosphamide) to arrest the scarring process.^[2]

Stem 4 — Name the autoantigen, its anatomical location, the salt-split localisation, and the usual first drug class for mild classical mechanobullous EBA.^[1]

AnswerShowHide

The autoantigen is type VII collagen, the major component of the anchoring fibrils at the dermal-epidermal junction. On salt-split skin the autoantibodies bind the FLOOR (dermal side), because type VII collagen sits below the lamina densa. For mild classical disease the anti-neutrophilic agents colchicine or dapsone come first; dapsone waits for a normal G6PD result.^{[1][2][13][14]}

References15ShowHide

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13. [13]Goyal N, Rao R, Shenoi SD, Pai S. Epidermolysis bullosa acquisita and anti-p200 pemphigoid as major subepidermal autoimmune bullous diseases diagnosed by floor binding on indirect immunofluorescence microscopy using human salt-split skin Indian J Dermatol Venereol Leprol, 2017.PMID 28749386
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