Bullous pemphigoid and pemphigus vulgaris are both autoimmune diseases that cause blistering of the skin, but they attack different structural targets and behave quite differently. In pemphigus vulgaris, the immune system produces antibodies against the proteins that glue skin cells to each other, causing fragile blisters within the upper layer of skin. In bullous pemphigoid, the antibodies instead target the proteins anchoring the skin’s outer layer to the tissue beneath it, producing tense, firm blisters at a deeper level.1Europe PMC. Mechanisms of Disease: Pemphigus and Bullous Pemphigoid That structural difference drives nearly every distinction between the two diseases, from what the blisters look and feel like to how dangerous each condition is.
Where the Blisters Form and Why It Matters
Your skin is built in layers. The outermost layer, the epidermis, is made of stacked cells held together by rivet-like junctions called desmosomes. Underneath, the epidermis is anchored to the deeper dermis by a different set of junctions along what’s called the basement membrane zone. Pemphigus vulgaris and bullous pemphigoid each sabotage one of these two anchoring systems.
In pemphigus vulgaris, the autoantibodies go after desmoglein 3, a protein that sits in those desmosomes and keeps neighboring skin cells stuck together. When antibodies bind desmoglein 3, the protein gets pulled off the cell surface and broken down inside the cell.2PubMed Central. p38MAPK signaling and desmoglein-3 internalization are linked events in pemphigus acantholysis Without it, cells detach from one another and round up individually, a process called acantholysis. The result is a blister that forms within the epidermis itself. Because that blister has only a thin, unsupported roof of skin cells, it’s extremely fragile. Pemphigus blisters rupture easily, often before a patient even notices them, leaving raw, painful erosions.
In bullous pemphigoid, the target is BP180, a transmembrane protein that helps anchor the bottom row of epidermal cells to the basement membrane below.3PubMed Central. BP180/Collagen XVII: A Molecular View When antibodies latch onto BP180, they trigger a complement-mediated inflammatory response, recruiting immune cells that cause tissue damage along the basement membrane zone.4Europe PMC. Mechanisms of Disease: Pemphigus and Bullous Pemphigoid The blister forms below the epidermis, meaning it has the full thickness of the epidermis as its roof. That makes bullous pemphigoid blisters noticeably tougher: they’re tense, dome-shaped, and can sit intact on the skin for days.
How They Look on the Skin
Clinically, these two diseases can look surprisingly different once you know what to watch for. Bullous pemphigoid typically presents as large, tense blisters on red or normal-looking skin, often on the arms, legs, and trunk. Many patients first notice intense itching, sometimes weeks before any blisters appear. The blisters themselves can be filled with clear or slightly blood-tinged fluid and often don’t rupture on their own for some time.
Pemphigus vulgaris is a different story. Because the blisters are so fragile, what patients and doctors often see are not intact blisters but raw, weeping erosions. A gentle lateral push on normal-looking skin near a lesion can shear off the top layer, a bedside finding known as the Nikolsky sign. Crucially, pemphigus vulgaris frequently involves the mucous membranes, especially the mouth. Many patients first develop painful oral erosions months before skin lesions appear, which often leads to misdiagnosis as canker sores or oral thrush. Bullous pemphigoid, by contrast, involves the mouth only rarely.
That mucosal involvement is one of the most reliable bedside clues. If someone walks in with mouth sores and fragile skin erosions, pemphigus vulgaris climbs to the top of the list. If they walk in with tense, itchy blisters on the limbs and trunk but a clean mouth, bullous pemphigoid is far more likely.
Under the Microscope
A skin biopsy confirms what the clinical picture suggests and helps rule out other blistering conditions. The pathologist sees two very different pictures. In pemphigus vulgaris, the biopsy shows an intraepithelial blister: the split is within the epidermis itself, with rounded-up, detached skin cells floating inside the blister cavity. The bottom row of cells typically remains attached to the basement membrane, giving a characteristic “tombstone” appearance.5The Lancet. Pemphigus and bullous pemphigoid
In bullous pemphigoid, the split is subepidermal, meaning the entire epidermis lifts cleanly off the dermis. The blister cavity and the tissue along the basement membrane are typically packed with inflammatory cells, particularly eosinophils.6The Lancet. Pemphigus and bullous pemphigoid – Section: Bullous pemphigoid That eosinophil-rich infiltrate is a useful pointer toward bullous pemphigoid even if the biopsy catches a pre-blister stage.
Immunofluorescence and Blood Tests
Routine biopsy shows where the blister forms, but immunofluorescence testing reveals the immune fingerprint. A second biopsy taken from skin next to a blister (not from the blister itself) is examined under fluorescent light after being treated with tagged antibodies. The pattern of glow is distinctive for each disease.
In pemphigus vulgaris, direct immunofluorescence shows IgG deposited in a lace-like or “fishnet” pattern between the epidermal cells, outlining the intercellular spaces where desmoglein sits.7PubMed Central. A Cross-sectional Study of Direct Immunofluorescence in the Diagnosis of Immunobullous Dermatoses In bullous pemphigoid, the glow appears as a smooth, linear band along the basement membrane zone, with IgG and complement (C3) deposited there.8PubMed Central. Direct Immunofluorescence in Immunobullous Disorders of Skin With Histopathological Correlation Among Patients Attending a Tertiary Care Center – Section: Results The difference is unmistakable to a trained eye: fishnet versus a solid line.
Blood tests add another layer. ELISA assays can detect and measure circulating antibodies against desmoglein 1 and desmoglein 3 (for pemphigus) or against BP180 (for bullous pemphigoid). These antibody levels tend to track with disease activity. Falling titers during treatment usually signal improvement, making ELISA useful not just for diagnosis but also for monitoring whether a patient is responding to therapy.9Medical Journal Armed Forces India. An observational study to determine the role of indirect immunofluorescence and ELISA for desmogleins in the diagnosis and monitoring of autoimmune bullous disorders Similarly, repeated testing for anti-BP180 antibodies in bullous pemphigoid patients can help guide treatment decisions over time.10PubMed Central. Diagnosis and clinical severity markers of bullous pemphigoid
Who Gets Each Disease
Bullous pemphigoid is considerably more common. A UK population-based study found an incidence of about 4.3 per 100,000 person-years for bullous pemphigoid, compared with roughly 0.7 per 100,000 for pemphigus vulgaris, making bullous pemphigoid about six times more frequent.11BMJ. Bullous pemphigoid and pemphigus vulgaris—incidence and mortality in the UK: population based cohort study Women outnumber men in both conditions.
The age profiles differ as well. In the same study, the median age at diagnosis for bullous pemphigoid was 80, firmly making it a disease of the elderly. Pemphigus vulgaris presented earlier, with a median age of 71, though it can appear at any adult age and occasionally in younger people too.12BMJ. Bullous pemphigoid and pemphigus vulgaris—incidence and mortality in the UK: population based cohort study Pemphigus vulgaris also has well-known ethnic and geographic clustering, with higher rates among people of Ashkenazi Jewish, Mediterranean, and South Asian descent, though the genetics behind that susceptibility are complex.
Drug Triggers
Both diseases can occasionally be triggered or unmasked by medications, though the drugs involved tend to differ. For pemphigus, a systematic review of 170 drug-induced cases found that penicillamine was by far the most common culprit, responsible for about a third of cases, followed by captopril and bucillamine. Other ACE inhibitors have also been implicated in case reports.13PubMed. Drug-induced pemphigus: A systematic review of 170 patients 14PubMed. Drug-related pemphigus and angiotensin converting enzyme inhibitors Many of these drug-triggered pemphigus cases are milder than the spontaneous form and may resolve after the offending medication is stopped.15PubMed. Drug-induced pemphigus: A systematic review of 170 patients
For bullous pemphigoid, the drugs flagged most often in recent years are DPP-4 inhibitors (gliptins), a class of diabetes medications, and immune checkpoint inhibitors used in cancer therapy. The association with gliptins has attracted particular attention because these drugs are widely prescribed in the elderly population that already carries the highest baseline risk for bullous pemphigoid. Recognizing a medication trigger matters practically, because stopping or switching the drug can sometimes bring the disease under control without heavy immunosuppression.
Treatment Differences and Overlap
Both diseases are treated with immunosuppression, but the intensity and drug choices aren’t identical. Systemic corticosteroids remain a mainstay for both, though bullous pemphigoid can sometimes be managed with potent topical steroids alone, especially in patients whose disease is limited. For pemphigus vulgaris, systemic treatment is almost always necessary because mucosal disease and widespread erosions rarely respond to topical therapy by itself.
When a steroid-sparing agent is needed, azathioprine and mycophenolate mofetil are the most common choices for both diseases. The two drugs appear roughly equally effective when combined with corticosteroids, though mycophenolate is generally better tolerated in terms of liver toxicity and bone marrow suppression.16PubMed. Immunosuppressive therapy for autoimmune bullous diseases
A major shift in pemphigus treatment has been the adoption of rituximab, which depletes the B cells that produce pathogenic antibodies. Rituximab is now approved as first-line therapy for pemphigus and has substantially improved outcomes, reducing the need for prolonged high-dose steroids.17PubMed. Immunotherapy for pemphigus and bullous pemphigoid For bullous pemphigoid, rituximab has shown benefit in severe or refractory cases but is not yet the standard first-line approach. Instead, newer agents targeting type 2 inflammation, such as dupilumab, have shown promising results in refractory bullous pemphigoid, reflecting the more prominent role of eosinophilic inflammation in that disease.18PubMed Central. Advancements in Bullous Pemphigoid Treatment: A Comprehensive Pipeline Update Neonatal Fc receptor antagonists such as efgartigimod, which lower circulating IgG levels, are also under investigation for both conditions.19PubMed Central. Advancements in Bullous Pemphigoid Treatment: A Comprehensive Pipeline Update
Complications, Infections, and Mortality
Before modern immunosuppression, pemphigus vulgaris was frequently fatal. The disease has become survivable with treatment, but mortality remains elevated. A study of pemphigus patients found overall mortality about 2.4 times higher than in the general population, driven largely by infections, particularly pneumonia and sepsis.20PubMed. Mortality and Cause of Death in Patients with Pemphigus That infection risk comes from two directions at once: the disease itself creates open wounds that serve as entry points for bacteria, and the immunosuppressive drugs used to treat it weaken the body’s ability to fight those infections.
Bullous pemphigoid carries its own serious risks, compounded by the fact that most patients are elderly and often have other medical problems. An analysis of hospitalized patients in the United States found that over half of inpatients with pemphigoid had a serious infection during their stay, compared with about a quarter of inpatients without these conditions. Infections were associated with substantially higher in-hospital mortality in both diseases.21PubMed. Association of serious infections with pemphigus and pemphigoid: analysis of the Nationwide Inpatient Sample – Section: RESULTS The challenge for clinicians treating bullous pemphigoid in the elderly is that corticosteroids, the first-line treatment, can themselves increase infection risk and worsen outcomes in frail patients.22PubMed Central. Bullous Pemphigoid Complicated by Sepsis
Wound care matters, too. Both diseases leave areas of denuded or fragile skin that need protection from trauma and microbial colonization. Non-adherent, moisture-retentive dressings are generally recommended to minimize further damage during bandage changes, particularly in elderly or high-risk patients.
The Neurological Link in Bullous Pemphigoid
One of the more unexpected findings in recent years is a strong association between bullous pemphigoid and neurological disease. Multiple population-based studies have found that patients with dementia, Parkinson’s disease, stroke, multiple sclerosis, and epilepsy develop bullous pemphigoid at significantly higher rates than the general population. A French case-control study of 868 bullous pemphigoid patients found odds ratios of 3.4 for dementia, 3.0 for Parkinson’s disease, and a striking 10.7 for multiple sclerosis compared with matched controls.23Journal of Investigative Dermatology. Bullous Pemphigoid and Neurological Diseases: A Population-Based Case–Control Study A Finnish registry study similarly found that patients with multiple sclerosis had nearly a sixfold higher risk of later developing bullous pemphigoid, and various forms of dementia carried two- to fourfold increases in risk.24Scientific Reports. Psychiatric and neurological disorders are associated with bullous pemphigoid – a nationwide Finnish Care Register study – Section: Results
The proposed explanation is intriguing. BP180, the same protein targeted by autoantibodies in bullous pemphigoid, is also expressed in neurons of the central nervous system. The theory is that neurological damage may expose BP180 to the immune system in the brain, breaking immune tolerance and eventually leading to an antibody response that also attacks BP180 in the skin. This remains a hypothesis rather than a proven mechanism, but the epidemiological association is consistent and strong across multiple studies and countries.25PubMed. Neurological disorders are associated with bullous pemphigoid – Section: RESULTS For caregivers of elderly patients with neurological conditions, new-onset itching or unexplained blisters should prompt consideration of bullous pemphigoid.
Pemphigus vulgaris does not share this neurological association. However, there are rare reports of pemphigus vulgaris occurring alongside myasthenia gravis and thymoma, a different kind of autoimmune overlap that seems to involve shared autoimmune susceptibility rather than a shared target protein.26PubMed. Immunologic studies of a case of myasthenia gravis associated with pemphigus vulgaris after thymomectomy
Pregnancy and Newborns
Both conditions can affect pregnancy, though in slightly different ways. When a pregnant woman has pemphigus vulgaris, her IgG autoantibodies against desmoglein 3 can cross the placenta and cause temporary blistering in the newborn, a condition called neonatal pemphigus.27PubMed. Neonatal pemphigus in an infant born to a mother with serologic evidence of both pemphigus vulgaris and gestational pemphigoid The condition is rare and self-limiting: once the maternal antibodies are cleared from the baby’s circulation over a few weeks, the blistering resolves.
Bullous pemphigoid itself is uncommon in women of childbearing age, but a related condition called pemphigoid gestationis (formerly “herpes gestationis,” despite having nothing to do with herpes) can appear during pregnancy. It targets the same BP180 protein and produces similar subepidermal blisters. In roughly one in ten cases, the antibodies cross the placenta and cause mild, transient blistering in the newborn.28PubMed Central. Diagnosis, fetal risk and treatment of pemphigoid gestationis in pregnancy: A case report – Section: Conclusion Pemphigoid gestationis typically flares around delivery and recurs in subsequent pregnancies, which distinguishes it from the garden-variety bullous pemphigoid of older adults.
How These Diseases Were Told Apart
Until the 1950s, nearly all blistering skin diseases were lumped under the umbrella term “pemphigus.” Clinicians recognized that some patients had fragile, mucosal-predominant blisters while others had tense blisters sparing the mouth, but without a way to identify the underlying mechanism, the distinction was largely clinical guesswork. The breakthrough came in the 1960s when researchers discovered that pemphigus patients carried circulating IgG antibodies targeting the surface of keratinocytes, while pemphigoid patients had IgG directed against the epidermal basement membrane, as demonstrated through indirect immunofluorescence.29Journal of Investigative Dermatology. Milestone 1 Autoimmune Bullous Diseases: Historical Perspectives – Section: Pemphigus That serological separation is what carved “pemphigoid” off as its own entity: the name literally means “pemphigus-like,” acknowledging the superficial resemblance while flagging a fundamentally different disease.
Modern diagnostic tools have refined the distinction far beyond what those early fluorescence studies could achieve. Today, ELISA panels can identify the specific protein target and quantify the antibody level in a single blood draw, allowing dermatologists to subtype the disease, predict severity, and track treatment response with a precision that would have been unimaginable when these conditions were first separated. The practical difference between the two diseases, once considered a matter of blister texture, now runs all the way from molecular target through treatment selection to long-term prognosis.