Most common autoimmune subepidermal blistering disease of the elderly; tense bullae on an urticarial base.
Also known as: BP, pemphigoid, subepidermal blistering
Overview
Chronic autoimmune subepidermal blistering disorder driven by IgG autoantibodies against hemidesmosomal antigens BP180 (BPAG2) and BP230 (BPAG1) at the dermoepidermal junction. Characterized by tense bullae on erythematous or urticarial skin, prominent pruritus, and infrequent mucosal involvement.
Epidemiology
Most common autoimmune blistering disease in Western countries. Incidence rises sharply with age; majority of patients >70. Slight female predominance. Increased risk in patients with neurologic disease (Parkinson disease, dementia, stroke, multiple sclerosis) and with use of DPP-4 inhibitors (gliptins) and immune checkpoint inhibitors.
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Question 1DermatologyMedium
A 58-year-old male has 3 months of severely pruritic blistering skin lesions on his trunk, extremities, and groin. Lesions are large, tense, fluid-filled bullae on normal-appearing or slightly erythematous skin that do not rupture easily. He is systemically well. Skin biopsy shows subepidermal blister with eosinophilic infiltrate. Direct immunofluorescence (DIF) shows linear IgG and C3 at the basement membrane zone. Which of the following is the most likely diagnosis?
ADermatitis herpetiformis
BPemphigus vulgaris
CBullous pemphigoid
DStevens-Johnson syndrome
Reveal answer & full explanation
Correct answer: C — Bullous pemphigoid
ADermatitis herpetiformis
BPemphigus vulgaris
CBullous pemphigoid✓
DStevens-Johnson syndrome
Why Bullous pemphigoid is correct
Tense, large bullae on normal or erythematous skin that do not rupture easily in an elderly patient are classic for bullous pemphigoid (BP)
Subepidermal blister with eosinophilic infiltrate on biopsy plus linear IgG and C3 at the basement membrane zone (BMZ) on direct immunofluorescence are diagnostic
Autoantibodies target BP180 (collagen XVII) and BP230 in the hemidesmosome, causing complement activation, neutrophil/eosinophil recruitment, and a subepidermal blister at the dermal-epidermal junction
Tense bullae occur because the subepidermal cleavage plane leaves an intact epidermal roof that withstands turgidity
Nikolsky sign is NEGATIVE in BP
Why the others are wrong
Dermatitis herpetiformis — shows granular IgA (not linear IgG/C3) and is associated with celiac disease; presents with grouped pruritic vesicles on extensor surfaces (confused-with, wrong immunofluorescence pattern)
Pemphigus vulgaris — intraepidermal acantholytic bullae that are flaccid and rupture easily into erosions, with intercellular ("chicken-wire") IgG and a positive Nikolsky sign (confused-with, wrong cleavage plane)
Stevens-Johnson syndrome — acute, drug-triggered mucocutaneous erosions with epidermal necrosis; not chronic and lacks the linear BMZ DIF pattern described (right-concept-wrong-setting)
Additional high-yield points
Bullous pemphigoid is the most common autoimmune blistering disorder; typically affects patients over 70 and is associated with neurologic disease (dementia, Parkinson disease, stroke)
Treatment: topical high-potency corticosteroids (clobetasol propionate 0.05%) — the BLISTER trial showed equivalence to systemic steroids with fewer side effects
Steroid-sparing options: doxycycline 100 mg BID plus niacinamide 1.5 g/day; azathioprine; mycophenolate; rituximab for refractory disease
Question 2DermatologyMedium
A 76-year-old woman is evaluated for a 6-week history of intractable itching followed by the appearance of large, tense fluid-filled blisters on her lower abdomen, inner thighs, and forearms. The blisters arise on urticarial plaques and remain intact when lateral pressure is applied. A lesional biopsy shows a subepidermal blister with an eosinophil-rich dermal infiltrate, and perilesional direct immunofluorescence reveals linear deposition of IgG and C3 along the basement membrane zone. To distinguish her condition from epidermolysis bullosa acquisita, salt-split skin direct immunofluorescence is performed. Which of the following findings best supports the suspected diagnosis?
AGranular IgA deposits within the dermal papillae tips
BIgG and C3 bind the dermal floor of the split skin
CIgG and C3 bind the epidermal roof of the split skin
DNetlike intraepidermal IgG between keratinocytes
Reveal answer & full explanation
Correct answer: C — IgG and C3 bind the epidermal roof of the split skin
AGranular IgA deposits within the dermal papillae tips
BIgG and C3 bind the dermal floor of the split skin
CIgG and C3 bind the epidermal roof of the split skin✓
DNetlike intraepidermal IgG between keratinocytes
Why IgG and C3 bind the epidermal roof of the split skin is correct
The clinical picture (elderly woman, prodromal pruritus, tense bullae on an urticarial base, subepidermal split with eosinophils, linear IgG/C3 at the basement membrane zone) is classic bullous pemphigoid.
Salt-split skin DIF cleaves the skin through the lamina lucida. In BP the target antigens BP180 (collagen XVII) and BP230 sit in the upper part of the basement membrane, so autoantibodies bind the epidermal (roof) side.
This is the single best discriminator from epidermolysis bullosa acquisita (EBA), whose antibodies target type VII collagen in the sublamina densa and therefore bind the dermal (floor) side.
Why the others are wrong
IgG and C3 binding the dermal floor of the split skin is the pattern of EBA (anti-type VII collagen); it is the exact entity the test is meant to exclude, so it argues against BP.
Granular IgA deposits within the dermal papillae tips are the hallmark of dermatitis herpetiformis, a celiac-associated disorder of young adults with grouped extensor vesicles, not subepidermal IgG/C3 disease in the elderly.
Netlike intraepidermal IgG between keratinocytes is the intercellular ("chicken-wire") pattern of anti-desmoglein pemphigus vulgaris, which produces flaccid bullae, painful oral erosions, a positive Nikolsky sign, and an intraepidermal split, all absent here.
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Recent UV exposure or radiotherapy (can trigger localized disease)
Pathophysiology
IgG autoantibodies bind BP180 (collagen XVII) at the NC16A domain and BP230 within the hemidesmosomal plaque. Complement activation, mast cell degranulation, and eosinophil recruitment release proteases that cleave the lamina lucida, producing subepidermal separation with preservation of the overlying epidermis (hence tense, intact bullae).
Clinical presentation
Symptoms
Severe generalized pruritus, often weeks to months before blisters appear (prodromal or non-bullous phase)
Tense fluid-filled blisters arising on urticarial or normal-appearing skin
Dermatitis herpetiformis — Intensely pruritic grouped vesicles on extensor surfaces in young adults; associated with celiac; granular IgA at dermal papillae
Epidermolysis bullosa acquisita — Blisters on trauma-prone sites, milia, scarring; antibodies to type VII collagen; salt-split skin binds dermal side
Linear IgA bullous dermatosis — "String of pearls" annular vesicles; vancomycin a common trigger; linear IgA at basement membrane on DIF
Bullous drug eruption / SJS/TEN — Acute onset after offending drug; targetoid lesions, mucosal involvement, full-thickness epidermal necrosis on biopsy
Bullous arthropod reaction — Localized clustered tense vesicles on exposed skin; preceding bite history; eosinophilic dermal infiltrate without antibody deposition
Diagnostic workup
Diagnostic criteria
Diagnosis requires clinical features plus histopathology and immunofluorescence. Lesional biopsy: subepidermal blister with eosinophil-rich dermal infiltrate. Perilesional DIF: linear deposition of IgG and C3 along the basement membrane zone. Salt-split skin DIF: antibodies bind the epidermal (roof) side, distinguishing BP from EBA.
Labs
Serum ELISA for anti-BP180 NC16A and anti-BP230 IgG (BP180 titers correlate with disease activity)
Review medication list with emphasis on DPP-4 inhibitors and checkpoint inhibitors
Imaging
No routine imaging; tailor to comorbid evaluation
Consider age-appropriate malignancy screening if atypical presentation, but routine paraneoplastic workup is not indicated
Diagnostic algorithm
flowchart TD
A[Elderly patient with<br/>itch ± tense bullae] --> B[Skin biopsy x2:<br/>lesional H&E +<br/>perilesional DIF]
B --> C{DIF: linear<br/>IgG/C3 at BMZ?}
C -->|Yes| D[Serum anti-BP180/BP230<br/>ELISA]
C -->|No| E[Consider PV, DH,<br/>EBA, LABD]
D --> F{Disease extent}
F -->|Localized / mild| G[Clobetasol 0.05%<br/>whole-body topical<br/>± doxycycline + niacinamide]
F -->|Moderate-severe| H[Prednisone 0.5 mg/kg<br/>+ steroid-sparing agent]
H --> I{Refractory?}
I -->|Yes| J[Rituximab,<br/>IVIG, omalizumab]
I -->|No| K[Slow taper<br/>over months]
Bullous pemphigoid — diagnostic and treatment pathway.
Treatment
First-line
Localized or mild disease: superpotent topical corticosteroid — clobetasol propionate 0.05% applied to the entire body 30-40 g/day (per Joly NEJM 2002 trial showing equivalent efficacy to oral steroids with fewer adverse events)
Moderate-to-severe disease: prednisone 0.5 mg/kg/day with taper as disease controls; goal taper to <10 mg/day within months
Tetracycline-class antibiotic (doxycycline 200 mg/day) with or without nicotinamide — comparable efficacy to oral prednisone in mild-moderate disease (BLISTER trial, Williams Lancet 2017)
Wound care and itch management; sedating antihistamines (hydroxyzine, diphenhydramine) cautiously in elderly
Rituximab for refractory or steroid-dependent disease
Omalizumab and dupilumab — emerging biologic options targeting IgE and IL-4/IL-13 pathways
Stop offending medication (DPP-4 inhibitor, checkpoint inhibitor where feasible)
Complications
Secondary bacterial infection, cellulitis, sepsis
Steroid morbidity in elderly: hyperglycemia, osteoporosis, fractures, delirium
Increased 1-year mortality (10-40% in elderly with comorbidities), often from infection or cardiovascular events rather than the disease itself
Recurrence after taper of therapy
PANCE pearls
Non-bullous prodromal phase can mimic chronic urticaria, scabies, or eczema for months before blisters appear; high index of suspicion in elderly patients with intractable itch.
Salt-split skin direct immunofluorescence distinguishes BP (epidermal/roof side) from epidermolysis bullosa acquisita (dermal/floor side).
Whole-body clobetasol is genuinely first-line for many elderly patients and avoids systemic steroid morbidity.
DPP-4 inhibitors — especially linagliptin and vildagliptin — are now a recognized iatrogenic trigger; switch class if BP develops.
Strong association with neurologic disease; ask about Parkinson disease, dementia, or stroke.
References
AAD/EADV 2022 — European S2k guidelines for the management of bullous pemphigoid (Borradori et al., JEADV 2022)
Joly NEJM 2002 — A comparison of oral and topical corticosteroids in patients with bullous pemphigoid (Joly et al., NEJM 2002)
BLISTER Trial — Doxycycline versus prednisolone as initial treatment for bullous pemphigoid (Williams et al., Lancet 2017)
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