Bullous Pemphigoid
Clinical Snapshot
Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease of the skin, driven by circulating and tissue-bound autoantibodies against BP180 (type XVII collagen) and/or BP230 - 2 structural proteins of the hemidesmosome that anchor the epidermis to the underlying dermis at the dermal-epidermal junction (DEJ).[1] Autoantibody binding activates complement (primarily through IgG1, generating C3 and a downstream membrane attack complex) alongside a parallel Th2-cytokine response (IL-4, IL-13, IL-31) that recruits eosinophils and mast cells to the DEJ. The combined effect strips the epidermis away from the dermis as a single intact sheet - a subepidermal split - which is why the resulting bullae are tense and do not extend or rupture with lateral pressure (a negative Nikolsky sign).[2]
This is the key feature distinguishing BP from pemphigus vulgaris, an entirely different disease in which autoantibodies against desmoglein 1 and 3 attack the connections between keratinocytes themselves, producing an intraepidermal split, flaccid and easily ruptured blisters, a positive Nikolsky sign, and prominent early mucosal (often oral) involvement - in contrast to BP, where mucosal disease is rare.[1]
BP is the most common autoimmune subepidermal blistering disease and predominantly affects the elderly: incidence in the general population is roughly 2.4-23 cases per million per year, rising about 10-fold to 190-232 cases per million per year in people 80 years and older, and overall incidence has increased approximately 2- to 4-fold over the past 2 decades as the population ages.[2] BP meaningfully reduces quality of life through severe, often relentless pruritus, and carries genuine mortality risk - a meta-analysis found a nearly 3-fold increase in 1-year standardized mortality compared with the general population.[3][2] A panel of 9 Canadian dermatologists published consensus recommendations for the diagnosis and management of BP specifically for the Canadian context in 2025, and this chapter follows that consensus closely, supplemented by the primary trial evidence it draws on.[2]
Recognize the Condition
The pre-bullous (prodromal) phase - easy to misdiagnose
BP often announces itself weeks to months before any blister appears, as intense, sometimes disabling pruritus accompanied by urticarial or eczematous-looking plaques, or excoriated papules - the itch is frequently out of proportion to how little the skin actually looks affected. This pre-bullous phase is very often mistaken for eczema, urticaria, a drug rash, or simply "itchy skin of old age," and the true diagnosis is only made once tense bullae appear, sometimes considerably later. Consider BP specifically whenever an older patient presents with new-onset pruritus, eczema-like change, or urticaria that does not behave like a typical case, especially with a plausible medication trigger (see Risk Factors).[2]
The classic bullous phase
The hallmark presentation is intensely pruritic, tense bullae, filled with clear or occasionally hemorrhagic fluid, arising on both inflamed (erythematous or urticarial) and entirely normal-appearing skin, typically in a symmetric distribution favouring the flexural surfaces - inner thighs, groin, axillae, forearms, and lower abdomen. The trunk and limbs are affected far more often than the face, which (along with the scalp) is frequently spared.[2] Older, ruptured bullae leave shallow erosions that, unlike pemphigus, tend to heal without significant scarring. Mucosal involvement is rare in classic BP - if mucosal disease is prominent, reconsider the diagnosis (see Assessment and Diagnosis).[2]
Non-classical presentations
A meaningful minority of patients never develop the classic picture above. Recognized non-classical patterns include:[2]
- Pauci-bullous or localized eczema-like disease - persistent, itchy, eczematous patches with few or no visible bullae.
- Localized disease, including pretibial BP confined to the lower legs.
- Dyshidrosiform (pompholyx-like) BP - small, deep-seated vesicles on the palms and soles.
- Prurigo nodularis-like BP - firm, intensely itchy nodules rather than blisters.
Because of this polymorphous presentation, maintain a genuinely wide differential (see Assessment and Diagnosis) rather than anchoring on "no blisters, so it can't be BP."
Risk Factors
- Age over 70 years is the single most important risk factor, and incidence rises roughly 10-fold again after age 80 - BP should be an active consideration for any older patient with new pruritus, eczema, or urticaria.[2]
- A personal history of a neurologic disorder - dementia, Parkinson disease, stroke, multiple sclerosis, or epilepsy - each shows an epidemiologic association with BP, though the underlying mechanism is not fully understood.[2]
- Active BP is itself pro-inflammatory and prothrombotic, raising the risk of venous thromboembolism compared with age-matched controls - relevant when weighing immobility, hospitalization, or additional VTE risk factors in an affected patient.[2]
- A number of medications are associated with an increased incidence of BP (medication-associated, or drug-induced, BP) - a thorough medication review is an essential part of the work-up in every newly diagnosed patient.[2]
Medications associated with bullous pemphigoid
The table below reflects medication classes with at least moderate-strength evidence of association, from the 2025 Canadian consensus.[2] A large UK case-control study and a separate systematic review/meta-analysis are the main sources of the odds ratios (ORs) cited.[4][5]
| Medication class | Examples | Strength of association |
|---|---|---|
| Immune checkpoint inhibitors (ICIs) - PD-1, PD-L1, and CTLA-4 inhibitors | Nivolumab, pembrolizumab, atezolizumab, ipilimumab | Moderate to high - multiple real-world studies; PD-1 inhibitors carry the highest risk within the class.[6][2] |
| DPP-4 inhibitors ("gliptins") | Linagliptin, saxagliptin, sitagliptin | Moderate - meta-analysis odds ratio 1.92 (95% CI 1.55-2.38) and a large case-control study odds ratio 2.77 (95% CI 2.37-3.23).[5][4] |
| Aldosterone antagonists | Spironolactone, eplerenone | Moderate to low, odds ratio 1.75 (95% CI 1.28-2.40).[5] |
| Antibiotics | Beta-lactams (e.g., penicillins), macrolides (e.g., erythromycin) | Moderate to low, odds ratio 2.08 (95% CI 1.99-2.17, adjusted).[4] |
| Antiparkinsonian medications | Anticholinergics (e.g., benztropine), odds ratio 3.12; dopaminergics (e.g., levodopa), odds ratio 2.03 | Moderate to low.[5] |
| Antidementia medications | Donepezil, galantamine, memantine | Moderate to low.[4] |
| Second-generation antipsychotics | Olanzapine, risperidone | Moderate to low, odds ratio 2.58 (95% CI 2.20-3.03).[4] |
The DPP-4 inhibitor signal is particularly relevant to pharmacists reviewing a diabetes regimen: it is consistent, replicated across multiple pharmacovigilance and case-control studies, and directly actionable (see Choose Initial Treatment and Special Populations for what to do once identified). For ICIs, roughly 30% of patients experience a cutaneous immune-related adverse event, and BP specifically develops in an estimated 3.5% of ICI-treated patients, with a median time to onset of about 22-29 weeks after starting therapy - though BP can also emerge after the ICI has already been stopped.[6][2] Even with a 2- to 3-fold increase in relative risk, BP linked to any of these medication classes remains rare in absolute terms, and there is no recommendation to avoid these drugs pre-emptively in a patient with no personal history of BP.[2]
Red Flags & Refer
Any of the following changes the urgency and/or the treatment plan:
- Extensive body-surface-area involvement, or disease a patient/caregiver genuinely cannot manage with topical treatment alone - this defines "extensive" rather than "limited" disease and is the trigger to move to systemic corticosteroid therapy rather than persisting with a topical-only regimen.[2]
- Secondary infection of eroded or denuded skin (localized cellulitis, or evolving sepsis) - extensive blistering and erosion in an elderly, often frail patient carries real physiologic parallels to a partial-thickness burn, and infection is a major driver of morbidity and mortality in this population.
- Lack of disease control after 2 weeks of appropriately dosed topical clobetasol (or an equivalent superpotent topical corticosteroid) - treat this as the signal to escalate to systemic therapy, not to switch to a different topical agent.[2]
- New bullae, worsening pruritus, or systemic symptoms in a patient already on a systemic corticosteroid or a steroid-sparing agent - reassess for inadequate dosing, non-adherence (topical non-adherence is common, especially in frail patients with reduced dexterity or mobility), or a missed alternative diagnosis before simply adding more immunosuppression.[2]
- A newly started, temporally plausible culprit medication - especially a DPP-4 inhibitor, but also an aldosterone antagonist, an antipsychotic, an antiparkinsonian agent, or an antibiotic - should prompt a structured medication review and, outside of immune checkpoint inhibitors, withdrawal of the suspected agent alongside standard BP treatment.[2]
- Suspected immune-checkpoint-inhibitor-induced BP in a patient on active cancer immunotherapy - do not stop the ICI unilaterally; this requires collaborative management with the treating oncology team (see Special Populations).[2]
- Any patient beginning long-term systemic corticosteroid therapy - proactively flag for the bone, gastrointestinal, glucose, and infection-risk monitoring detailed in Monitoring and Follow-Up; serious corticosteroid-related adverse events, including osteoporotic fracture, can occur even at doses of 5 mg/day or less.[2]
Assessment & Diagnosis
Diagnostic approach
Diagnosis of classic BP rests on the combination of clinical morphology, compatible histopathology, and confirmatory immunofluorescence and/or serology - no single test is used in isolation.[2]
| Presentation | Clinical criteria | Histopathological/serological criteria |
|---|---|---|
| Classical | 3 of 4: age over 70 years; no atrophic scarring; no mucosal involvement; no predominant bullous lesions on the neck/head | Positive DIF (linear IgG and/or C3 along the DEJ) and anti-basement-membrane-zone antibodies by indirect immunofluorescence (IIF) and/or anti-BP180/anti-BP230 IgG by ELISA or similar |
| Non-classical | No validated criteria - high suspicion with pruritus, urticarial, or eczematous eruption | Same as above |
| Negative or unavailable DIF | A consistent clinical picture (e.g., tense blisters) | Consistent histopathology (subepidermal split with an eosinophil-rich infiltrate on H&E) and anti-BMZ antibodies by IIF and/or anti-BP180/anti-BP230 IgG by ELISA |
Biopsy technique
Take 2 separate biopsies. For routine histopathology (hematoxylin and eosin), biopsy the edge of a fresh, intact bulla - this typically shows a subepidermal split with an eosinophil-predominant inflammatory infiltrate. For direct immunofluorescence (DIF), biopsy perilesional skin (erythematous skin adjacent to a lesion is acceptable, but never a bulla itself) and place it in Michel's medium or saline - never formalin or another aldehyde-based fixative, which causes false-negative DIF results.[2] DIF classically shows linear deposits of IgG and/or C3 along the DEJ; the precise location and serration pattern of these deposits can help distinguish BP from other subepidermal immunobullous diseases. If BP is strongly suspected clinically but the initial DIF is negative or equivocal, repeat the biopsy for DIF rather than abandoning the diagnosis.[2]
Serology and its diagnostic performance
Circulating autoantibodies can be detected by indirect immunofluorescence on salt-split skin (IIF), which localizes IgG binding to the epidermal (roof) side of the artificially separated DEJ in BP - a key distinguishing feature from epidermolysis bullosa acquisita, in which binding localizes to the dermal (floor) side instead - or by ELISA for anti-BP180 (NC16A domain) or anti-BP230 IgG.[2] A single-centre study of 1,125 patients reported the following diagnostic performance:[2]
| Method | Sensitivity | Specificity |
|---|---|---|
| DIF | 88.3% | 99.2% |
| IIF (salt-split skin) | 77.0% | 99.9% |
| ELISA, anti-BP180 (NC16A) | 70.0% | 89.8% |
| ELISA, anti-BP230 | 44.6% | 92.8% |
DIF has the best combined sensitivity and specificity and remains essential to a correct diagnosis in almost every case; serology is a valuable adjunct, particularly when DIF is unavailable, negative, or equivocal.[2]
Differential diagnosis
Given how polymorphous BP can look, keep a genuinely wide differential:[2]
- Pemphigus vulgaris - intraepidermal (not subepidermal) split, flaccid blisters, a positive Nikolsky sign, and prominent early mucosal (often oral) involvement - the single most important condition to distinguish from BP, since both the pathophysiology and the first-line topical approach differ.
- Pemphigus herpetiformis, dermatitis herpetiformis, linear IgA bullous dermatosis, bullous lichen planus, epidermolysis bullosa acquisita, bullous lupus erythematosus, and pemphigus foliaceus.
- For non-classic (pauci-bullous, eczema-like, or urticarial) presentations specifically: ordinary eczema, urticaria, prurigo nodularis, impetigo, erythema multiforme, Sweet syndrome, and Stevens-Johnson syndrome/toxic epidermal necrolysis (see that chapter) - and, in pregnancy, pemphigoid gestationis, a distinct disease (see Special Populations).
Associated work-up
A thorough medication review is essential at diagnosis, given the medication associations in Risk Factors. The association between BP and malignancy remains unclear in the literature; routine, extensive malignancy screening beyond age-appropriate cancer screening is not warranted unless prompted by specific symptoms.[2]
Treatment Targets
- Prevent the development of new bullae and lesions.
- Heal existing lesions and erosions.
- Alleviate patient-reported symptoms - pruritus and pain - which may not correlate closely with the visible extent or number of blisters, so ask about them directly rather than relying on inspection alone.[2]
- Minimize treatment-related morbidity and mortality - a goal in its own right, since BP predominantly affects elderly and often frail patients in whom the treatment (particularly high-dose systemic corticosteroids) can carry real risk.[2]
- Reach control of disease activity (CDA) - the point at which new lesions and pruritic symptoms stop forming and existing lesions begin to heal - as the working treatment milestone, since no single validated severity scale has proven practical for routine clinical use.[2]
Jointly decide with the patient (and caregiver, where relevant) what counts as "limited" disease that can realistically be managed with topical treatment alone, versus "extensive" disease warranting systemic therapy - this depends as much on the extent/location of disease and the practical time and effort of daily topical application (and whether a capable care partner is available) as on body-surface-area alone.[2]
Choose Initial Treatment
Topical vs. systemic - the first branch point
1st line, when practical topical clobetasol propionate 0.05% cream, applied once or twice daily to a maximum of 20 g/day, to all affected areas except the face (usually spared in BP) and skin folds (prone to atrophy) - a systematic review of 14 studies confirms it is effective and safe, and a randomized trial found the topical regimen achieved control of disease activity in more patients at 3 weeks, with fewer severe adverse events and lower mortality than oral prednisone - a safety benefit most pronounced in patients with extensive disease.[7][2] Moderate-certainty evidence shows a lower cumulative dose (10-30 g/day, tapered over 4 months) works as well, with a similar adverse-effect profile, as the historical standard (40 g/day, tapered over 12 months).[2] Lack of control after 2 weeks of topical clobetasol is the signal to escalate to systemic therapy - not to switch to a different topical class; there is no good evidence to support topical calcineurin inhibitors or topical JAK inhibitors as a substitute.[2]
1st line, when topical-only is not practical prednisone 0.5-1.0 mg/kg/day PO. Topical application over a large body-surface area can require 30-45 minutes of dedicated caregiver or nursing time per application - genuinely impractical for many community-dwelling Canadian patients without inpatient or community nursing support, which is why systemic therapy is often the realistic first-line choice in this setting.[2] Start at 0.5 mg/kg/day, which achieves control of disease activity in 69-75% of patients with milder disease by 3 weeks and carries a more favourable safety profile than higher starting doses, though it is less effective in more extensive disease; escalate toward 0.75-1.0 mg/kg/day if control is not achieved within 1-3 weeks (trial data show no added benefit of 1.25 mg/kg/day over 0.75 mg/kg/day).[2]
Tapering once disease control is achieved
Begin tapering roughly 2-3 weeks after control of disease activity is reached, and continue on the following schedules, adopted directly from the EADV guideline:[2][8]
- Topical corticosteroid: taper application frequency over 4-12 months, in phases of at least 1 month each - daily, then every 2 days, then twice weekly, then once weekly.
- Oral corticosteroid: gradually reduce to 0.1 mg/kg/day within 4-6 months of starting; therapy may then be discontinued after 3-6 months disease-free at this minimal dose.
Before starting an immunosuppressive agent
Screen for infection risk as usual before starting systemic corticosteroids or another immunosuppressant. Confirm age-appropriate vaccination status where practical, but do not delay treatment of acute BP for this. Perform tuberculosis skin testing as early as possible - within 1 month of starting therapy - for any patient starting a prednisone-equivalent dose of 15 mg/day or more.[2]
Steroid-sparing agents - preferred for long-term systemic therapy
Use a steroid-sparing agent for essentially every patient needing more than a short systemic corticosteroid course - either started concomitantly with corticosteroids to accelerate a safe taper, or added when combined topical-plus-systemic therapy is not achieving control, or continued for maintenance once the corticosteroid has been tapered off.[2]
First-choice steroid-sparing agent dupilumab 600 mg SC loading dose, then 300 mg SC every 2 weeks - favoured for its anticipated efficacy, low rate of adverse effects, and lack of clinically significant drug-drug interactions, which matters given how often BP patients are on multiple other medications. Consider starting concomitantly with oral corticosteroids (with tapering beginning no later than 6 weeks after initiation), using it after first-line treatment has failed, or specifically when a patient has safety concerns or contraindications to systemic corticosteroids. In the LIBERTY-BP ADEPT phase 2/3 trial, dupilumab plus a standard-of-care corticosteroid taper produced significantly higher remission rates at 16 and 36 weeks, a lower relapse rate, and less need for rescue therapy than placebo plus the same taper, with a safety profile consistent with dupilumab's established profile.[2]
Alternative steroid-sparing agents low-dose methotrexate 10-25 mg once weekly (occasionally as low as 5 mg weekly), azathioprine 0.5-2.5 mg/kg/day, mycophenolate mofetil 2-3 g/day, or omalizumab 300 mg every 4 weeks.[2] Methotrexate combined with an initial short course of topical clobetasol reduces the duration of high-potency topical treatment needed and lowers relapse at 9 months compared with topical treatment alone (25% vs. 42.5% in a randomized non-inferiority trial) - but current Canadian product labelling states methotrexate should be avoided when estimated glomerular filtration rate (eGFR) is under 50 mL/min/1.73 m².[2] Azathioprine and mycophenolate mofetil have broadly comparable efficacy in head-to-head data, but mycophenolate mofetil is better tolerated, with significantly lower liver toxicity - dose azathioprine according to thiopurine methyltransferase (TPMT) activity where available.[2] Omalizumab may be considered after first-line treatments have failed; evidence is limited to case series and retrospective studies, and its effect may be more pronounced with a higher baseline IgE level, though this is not firmly established.[2]
Adjunctive throughout treatment doxycycline 200 mg/day. A pragmatic, non-inferiority randomized trial compared doxycycline 200 mg/day against prednisolone 0.5 mg/kg/day as first-line monotherapy; doxycycline was associated with fewer severe, life-threatening, or fatal events, but some efficacy outcomes (including the proportion of patients completely blister-free at 6 weeks) favoured prednisolone, and patients on doxycycline needed more supplemental topical corticosteroid for symptom control.[9] The Canadian panel did not reach consensus on doxycycline as a first-line monotherapy alternative to corticosteroids, but does support its use as an adjunctive therapy throughout the treatment course.[2] Nicotinamide 500 mg up to 3 times daily is considered a low-risk, discretionary addition to doxycycline, though no trial confirms it adds benefit.[2]
Special situation dapsone, started at 50 mg/day and escalated gradually to a maximum of 200 mg/day based on tolerability, particularly for neutrophil-rich disease or for a patient already heavily immunosuppressed or ineligible for other steroid-sparing agents. Evidence is limited to case series; screen and monitor hematologically throughout treatment.[2]
Reserved for treatment failure rituximab and intravenous immunoglobulin (IVIG) are both highly effective, but given a real risk of serious adverse events (particularly in older patients), should in most cases be reserved for patients in whom multiple prior treatments have failed.[2] JAK inhibitors (baricitinib 4 mg/day, tofacitinib 5-10 mg twice daily, or upadacitinib 15 mg/day) have case-report-level evidence only, with no registered clinical trials at the time of the Canadian consensus; the panel did not reach consensus recommending them, and they should be considered only after other treatment options have been exhausted.[2]
Stopping a steroid-sparing agent
There is no evidence-based standard timeline for withdrawal. If discontinuation is a shared goal, consider a gradual taper only once the patient has been completely disease-free, with no new symptoms or flares, for at least 6 months.[2]
Non-Pharmacologic Treatment
Skin and wound care
- Handle fragile, blistered, or eroded skin gently - avoid friction and shearing forces during transfers, dressing changes, and routine care, particularly in a bedridden or low-mobility patient.
- Use non-adherent dressings over eroded areas; large, tense bullae may be drained (leaving the blister roof intact as a natural biological dressing) at the discretion of the treating clinician, though this is not itself a treatment for the underlying disease.
- Monitor closely for signs of secondary bacterial infection in denuded skin (see Red Flags) - extensive erosions carry real fluid, protein, and thermoregulatory losses, conceptually similar to a partial-thickness burn.
Itch management
Pruritus is often the most distressing symptom and, notably, does not reliably correlate with the number or activity of visible blisters - ask about it directly rather than judging severity from the skin alone.[2] Simple non-drug measures - lukewarm (not hot) bathing, fragrance-free emollients, loose, breathable clothing, and avoiding known individual triggers - provide modest but genuine relief alongside definitive treatment of the underlying disease.
Monitoring tools
No single validated severity scale has proven practical for routine clinical use. Consider the Itch Numeric Rating Scale (Itch NRS) for tracking pruritus in individual patients; the Bullous Pemphigoid Disease Area Index (BPDAI) and the Autoimmune Bullous Skin Disorder Intensity Score are more useful in research settings. A simple daily blister count has also been suggested as a practical activity measure some patients and caregivers can track at home.[2]
Supporting adherence
Non-adherence to topical treatment is more common than with other routes of administration and is linked to worse clinical outcomes - a combination of patient, treatment, and disease factors drives this, and rates are often highest in elderly patients who have physical difficulty applying medication over a large body-surface area.[2] Involve a caregiver early wherever one is available, keep the regimen as simple as realistically possible, and revisit whether a topical-only plan is still practical at each visit rather than assuming it remains so (see Choose Initial Treatment).
Patient and caregiver education
- Set expectations early: BP is a chronic, relapsing-remitting disease, and treatment courses commonly run for many months to over a year - this is not a "quick course of cream" condition.
- Explain that stopping topical or systemic treatment abruptly, rather than following the planned taper, risks a disease flare.
- Review the specific signs that should prompt the patient or caregiver to seek care promptly (see Red Flags).
- Coordinate explicitly with the patient's primary care or geriatric care team for monitoring items that fall outside dermatologic scope - bone health, glucose, blood pressure, and general frailty assessment are genuinely shared responsibilities.[2]
Special Populations
Elderly and frail patients
Because BP itself is predominantly a disease of older, often multi-morbid patients, minimize systemic corticosteroid exposure as early as is clinically reasonable.[2] Preferred dupilumab as first-choice therapy where available, given its favourable safety profile and lack of clinically significant drug-drug interactions; consider omalizumab if dupilumab is not effective or accessible, and methotrexate if not contraindicated. Avoid azathioprine in this population given hepatotoxicity risk - mycophenolate mofetil may be considered instead in appropriate scenarios. Rituximab and IVIG remain later-line options, with added caution for volume overload and other infusion-related adverse effects in frail patients.[2]
Active malignancy, including immune-checkpoint-inhibitor-associated BP
Manage BP in a patient with active malignancy in close collaboration with the treating oncology team, though dermatology will often have more direct experience with both BP itself and with biologic therapy, and should generally lead these treatment discussions.[2] Preferred dupilumab as first-line therapy here too, since systemic corticosteroids are frequently undesirable in a patient on active immunotherapy. Use with extreme caution rituximab in this group - though current data do not suggest it increases the risk of a second primary malignancy.[2] Specifically consider medication-induced BP in any patient on an ICI (anti-PD-1, anti-PD-L1, or anti-CTLA-4 - see Risk Factors). If the ICI is withheld because of BP, re-challenge can be considered once control of disease activity is achieved, ideally continuing a steroid-sparing agent such as dupilumab through the re-challenge to maintain control; even so, BP results in permanent ICI discontinuation in over half of cases.[2]
Pregnancy
Evaluate any pregnant patient with new blistering carefully for pemphigoid gestationis, a distinct, pregnancy-specific autoimmune blistering disease that must be distinguished from true BP occurring coincidentally during pregnancy.[2] Many standard BP therapies can be used in pregnancy, but agents with known fetal risk - specifically methotrexate and mycophenolate mofetil - should be avoided.[2] Discuss the risk-benefit profile of the remaining options with the patient and their obstetric team.
Children and adolescents
Childhood BP is rare, with 1 incidence peak in the first year of life and a second at a median age of about 8 years; mucosal involvement is more likely in early adolescence (roughly 10-13 years).[2] Infantile BP commonly affects acral sites (hands and feet), while older children are more likely to have external genital involvement and less likely to have hand/foot involvement. Histopathology is similar to adult disease. Evidence supporting treatment is limited to case reports, but systemic corticosteroids are effective in most reported cases and may be supplemented with methotrexate, dapsone, doxycycline, or mycophenolate, dosed by weight and/or age; isolated case reports support dupilumab in adolescents and cyclosporine in infants. Reserve azathioprine, IVIG, and rituximab for resistant pediatric cases. Use topical corticosteroids with the usual pediatric precautions.[2]
Renal impairment
Avoid methotrexate when eGFR is under 50 mL/min/1.73 m², per current Canadian product labelling; some data suggest careful use with dose reduction (as low as 5-10 mg/week) may be reasonable down to an eGFR of about 45 mL/min/1.73 m² in appropriately monitored patients, but the labelled threshold should guide routine practice.[2] Rituximab and IVIG carry their own renal considerations (IVIG in particular can cause renal dysfunction) - dose and monitor per specialist direction.
Hepatic impairment
Azathioprine and methotrexate both carry hepatotoxicity risk and need closer monitoring, or an alternative agent, in significant hepatic impairment; mycophenolate mofetil's lower liver-toxicity profile may make it the more suitable choice in this situation.[2]
Monitoring & Follow-Up
Monitoring systemic corticosteroid therapy
Patients with BP are frequently at high risk for corticosteroid-related adverse events - including osteoporotic fracture and serious infection - and these can occur at doses of 5 mg/day or less.[2] For any patient beginning long-term systemic corticosteroids:
- Consider vitamin D supplementation, adequate calcium intake (ideally from dietary sources), and bisphosphonate therapy for fracture prevention, alongside usual bone-density monitoring.[2]
- Monitor blood pressure and blood glucose regularly.[2]
- Manage predictable adverse effects per routine practice - for example, a proton pump inhibitor for corticosteroid-related gastroesophageal reflux.[2]
- Coordinate this monitoring explicitly with the patient's primary care team, since much of it falls outside dermatologic scope.[2]
Monitoring steroid-sparing agents
- Methotrexate: routine toxicity monitoring (CBC, liver enzymes, renal function) per usual practice; confirm eGFR before each dose adjustment.
- Azathioprine: dose according to TPMT activity where available; monitor CBC and liver enzymes regularly.
- Mycophenolate mofetil: monitor CBC and for signs of infection.
- Dapsone: screen before initiation and monitor hematologically throughout - watch specifically for hemolysis and methemoglobinemia.
- Rituximab/IVIG: monitor per specialist-directed infusion protocol, with particular attention to infusion reactions and, for IVIG, fluid status and renal function.
Disease-activity follow-up
Track patient-reported pruritus and pain alongside the visible extent of skin disease at every visit - these do not always move together.[2] A daily blister count, kept by the patient or caregiver, is a simple, practical activity measure between visits. Reassess whether a topical-only regimen is still realistic at each visit, rather than assuming it remains so once initially agreed upon.[2] If a steroid-sparing agent is being tapered or discontinued, do so only once the patient has been completely disease-free, with no new symptoms or flares, for at least 6 months.[2]
Common Errors to Avoid
- Dismissing an older patient's new, severe pruritus with urticarial or eczematous plaques as "just eczema" or "senile pruritus" without considering the pre-bullous phase of BP, especially when a plausible culprit medication is present.
- Continuing to treat with topical corticosteroid alone for more than 2 weeks without disease control, rather than escalating to systemic therapy at that point.
- Treating a patient's stated pruritus or pain as adequately controlled based on the visible extent of blistering alone - the 2 do not reliably correlate.
- Choosing azathioprine over mycophenolate mofetil by default in an elderly or frail patient without weighing azathioprine's greater hepatotoxicity risk in this population.
- Prescribing methotrexate without checking eGFR, or continuing it despite eGFR falling under 50 mL/min/1.73 m².
- Missing a medication-associated cause - particularly a DPP-4 inhibitor - during medication reconciliation, and treating BP purely as "idiopathic" without a structured review.
- Stopping an immune checkpoint inhibitor unilaterally for suspected ICI-associated BP without involving the treating oncology team.
- Starting long-term systemic corticosteroids without arranging bone, gastrointestinal, glucose, and blood-pressure monitoring, on the assumption that "low-dose" steroids are risk-free - clinically significant adverse events, including fracture, occur even at 5 mg/day or less.
- Assuming a topical-only regimen agreed at diagnosis remains practical indefinitely, rather than reassessing feasibility (dexterity, mobility, caregiver support) at each visit.
- Reaching for rituximab, IVIG, or a JAK inhibitor before a genuine trial of first-line and alternative steroid-sparing agents, rather than reserving these for truly refractory disease.
- Missing mucosal involvement, atrophic scarring, or facial/scalp-predominant bullous lesions and continuing to diagnose "classic BP" rather than reconsidering pemphigus vulgaris or another blistering disease.
Clinical Decision Algorithm
Drug Tables
How to use this table: doses are adult doses and require patient-specific confirmation, including renal/hepatic adjustment. Select any drug name to open its complete Pharmasist Drug Database page.
Topical Corticosteroid (First-Line)
First-line whenever practical, and an ongoing adjunct to systemic therapy. Lack of control after 2 weeks is the signal to escalate to systemic therapy, not to switch topical agents.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Clobetasol propionate | Initial: Apply once or twice daily to affected areas, excluding the face and folds Maximum: 20 g/day | Skin atrophy, striae, telangiectasia with prolonged use; systemic absorption possible with extensive-area or occlusive use | None significant with topical use at recommended doses | Avoid the face (usually spared in BP) and skin folds (prone to atrophy). A lower cumulative dose (10-30 g/day, tapered over 4 months) is as effective as the historical standard (40 g/day, tapered over 12 months). |
Systemic Corticosteroid
First-line when a topical-only regimen is not practical (extensive disease, or insufficient caregiver/nursing time for large-area topical application).
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Prednisone | Initial: 0.5 mg/kg/day PO Escalation: 0.75-1.0 mg/kg/day if control is not achieved in 1-3 weeks Taper: Reduce to 0.1 mg/kg/day within 4-6 months; may discontinue after 3-6 months disease-free at this dose | Hyperglycemia, hypertension, osteoporosis, GI upset, mood changes, infection risk, adrenal suppression with prolonged use | Additive hyperglycemia with other diabetogenic drugs; reduced vaccine response during immunosuppressive dosing | Arrange bone, GI, glucose, and blood pressure monitoring per Monitoring and Follow-Up. Begin tapering about 2-3 weeks after disease control is achieved. |
Steroid-Sparing Biologics
Dupilumab is the first-choice steroid-sparing agent given its favourable safety profile and minimal drug interactions; omalizumab is an alternative after 1st-line treatment failure.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Dupilumab | Loading dose: 600 mg SC once Maintenance: 300 mg SC every 2 weeks | Injection-site reaction, conjunctivitis, rarely eosinophilia | None clinically significant — a key reason it is favoured in patients on multiple other medications | May be started concomitantly with an oral corticosteroid, with tapering beginning no later than 6 weeks after initiation. |
| Omalizumab | Maintenance: 300 mg SC every 4 weeks | Injection-site reaction, rarely anaphylaxis | None significant | Evidence limited to case series and retrospective data. Effect may be more pronounced with a higher baseline IgE level, though this is not firmly established. |
Conventional Immunosuppressants (Steroid-Sparing)
Consider starting concomitantly with systemic corticosteroids to facilitate a safe taper.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Methotrexate | Initial: 10-25 mg PO or SC once weekly (occasionally as low as 5 mg weekly) Supportive care: Give with folic acid per usual practice | Hepatotoxicity, myelosuppression, GI upset, mucositis, rare pulmonary toxicity | Increased toxicity with NSAIDs, trimethoprim-sulfamethoxazole, and other folate antagonists | Avoid when eGFR is under 50 mL/min/1.73 m² per current Canadian labelling. Combined with an initial short course of clobetasol, it shortens the topical treatment duration needed and lowers relapse at 9 months. |
| Azathioprine | Adults: 0.5-2.5 mg/kg/day PO | Myelosuppression, hepatotoxicity, GI upset, increased malignancy risk with long-term use | Severe myelosuppression with allopurinol (reduce azathioprine dose substantially if co-administered); reduced efficacy of warfarin | Dose according to thiopurine methyltransferase (TPMT) activity where available. Avoid in elderly or frail patients given hepatotoxicity risk — consider mycophenolate mofetil instead. |
| Mycophenolate mofetil | Adults: 2-3 g/day PO in divided doses | GI upset (diarrhea common), myelosuppression, increased infection risk | Reduced absorption with antacids or cholestyramine; avoid live vaccines during treatment | Comparable efficacy to azathioprine, with significantly less liver toxicity — often the preferred alternative immunosuppressant. |
| Dapsone | Initial: 50 mg/day PO Titration: Escalate gradually to a maximum of 200 mg/day based on tolerability | Hemolysis (especially with G6PD deficiency), methemoglobinemia, agranulocytosis, peripheral neuropathy | Increased hematologic toxicity with other bone-marrow suppressants; trimethoprim increases levels of both drugs | Consider for neutrophil-rich disease, or when a patient is heavily immunosuppressed or ineligible for other steroid-sparing agents. Screen appropriately before initiation and monitor hematologically throughout. |
Adjunctive Antibiotic Therapy
Not recommended as first-line monotherapy by the Canadian panel, but supported as an ongoing adjunct throughout the treatment course.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Doxycycline | Adults: 200 mg/day PO, ongoing throughout treatment | GI upset, photosensitivity, esophageal irritation | Chelation with antacids, calcium, iron, or dairy reduces absorption | In a randomized non-inferiority trial against prednisolone 0.5 mg/kg/day as first-line monotherapy, doxycycline showed fewer severe/life-threatening/fatal events but a lower complete-blister-free rate at 6 weeks and higher supplemental topical steroid use. |
| Nicotinamide | Adults: Up to 500 mg PO 3 times daily | GI upset, flushing at high doses | None significant at this dose | A low-risk, discretionary addition to doxycycline — no trial confirms it adds benefit. |
Reserved for Refractory Disease
Given the risk of serious adverse events, particularly in older patients, reserve these agents for after multiple prior treatments (steroid-sparing agents above) have failed.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Rituximab | Dosing: Per specialist-directed protocol | Infusion reactions, infection risk, hypogammaglobulinemia, rare progressive multifocal leukoencephalopathy | Avoid live vaccines during and after treatment per usual practice | Does not appear to increase the risk of a second primary malignancy. Use with extreme caution in patients with active malignancy. |
| Immunoglobulin (human), IV | Dosing: Per specialist-directed protocol | Headache, aseptic meningitis, renal dysfunction, thrombosis, hemolysis | May blunt live-vaccine response for a period afterward | Premedicate for infusion reactions and ensure adequate hydration per usual IVIG practice. |
| Baricitinib | Reported dose: 4 mg/day PO | Infection risk, venous thromboembolism, malignancy (class warning), rare GI perforation | Avoid with potent OATP1B1/OATP1B3 inhibitors and other immunosuppressants | Case-report-level evidence only; the Canadian panel did not reach consensus recommending JAK inhibitors. Consider only after other options have been exhausted. |
| Tofacitinib | Reported dose: 5-10 mg PO twice daily | Infection risk, venous thromboembolism, malignancy (class warning), rare GI perforation | Avoid with potent CYP3A4 inhibitors/inducers and other immunosuppressants | Case-report-level evidence only, both as monotherapy and combined with systemic corticosteroids, often after failure of prednisone, minocycline, or dupilumab. |
| Upadacitinib | Reported dose: 15 mg/day PO | Infection risk, venous thromboembolism, malignancy (class warning), rare GI perforation | Avoid with potent CYP3A4 inhibitors and other immunosuppressants | Case-report-level evidence only, including after failure of high-dose prednisone. |
References
- Bullous pemphigoid — Anais Brasileiros de Dermatologia (Miyamoto D, Santi CG, Aoki V, Maruta CW). An Bras Dermatol 2019;94(2):133-146
- Navigating Bullous Pemphigoid: Consensus Recommendations for Diagnosis and Management-A Canadian Perspective — Journal of Cutaneous Medicine and Surgery (Lovegrove FE, Sauder MB, Mufti A, Beecker J, Dutz JP, Kirchhof MG, Mydlarski PR, Purdy KS, Lansang P). J Cutan Med Surg 2025;29(6):661-674
- Mixed Individual-Aggregate Data on All-Cause Mortality in Bullous Pemphigoid: A Meta-analysis — JAMA Dermatology (Tedbirt B, Gillibert A, Andrieu E, et al.). JAMA Dermatol 2021;157(4):421
- Association between drugs and vaccines commonly prescribed to older people and bullous pemphigoid: a case-control study — British Journal of Dermatology (Swiderski M, Vinogradova Y, Knaggs RD, et al.). Br J Dermatol 2025;192(3):440-449
- Association Between Medication Use and Bullous Pemphigoid: A Systematic Review and Meta-analysis — JAMA Dermatology (Liu SD, Chen WT, Chi CC). JAMA Dermatol 2020;156(8):891
- Association of Bullous Pemphigoid with Immune Checkpoint Inhibitor Therapy in Patients With Cancer: A Systematic Review — JAMA Dermatology (Asdourian MS, Shah N, Jacoby TV, Reynolds KL, Chen ST). JAMA Dermatol 2022;158(8):933
- A Comparison of Oral and Topical Corticosteroids in Patients with Bullous Pemphigoid — New England Journal of Medicine (Joly P, Roujeau JC, Benichou J, et al.). N Engl J Med 2002;346(5):321-327
- Updated S2K guidelines for the management of bullous pemphigoid initiated by the European Academy of Dermatology and Venereology (EADV) — Journal of the European Academy of Dermatology and Venereology (Borradori L, Van Beek N, Feliciani C, et al.). J Eur Acad Dermatol Venereol 2022;36(10):1689-1704
- Doxycycline versus prednisolone as an initial treatment strategy for bullous pemphigoid: a pragmatic, non-inferiority, randomised controlled trial — The Lancet (Williams HC, Wojnarowska F, Kirtschig G, et al.). Lancet 2017;389(10079):1630-1638
Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.