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Leiferman
Epidermolysis bullosa acquisita (EBA) is a rare autoantibody-associated blistering disease characterized by the presence of antibodies that target type VII collagen. Type VII collagen is a major component of anchoring fibrils in the epithelial basement membrane zone (BMZ) that attach the epidermis and epithelium to the underlying connective tissue. Immune-mediated disruption likely accounts for the separation of the dermis and epidermis that underlies the clinical presentation of skin fragility and blistering. EBA may affect the skin and/or mucous membranes. Nail dystrophy and scarring alopecia may also develop.
Clinical presentations vary widely and are often similar to those of other immunobullous diseases. Because of the overlapping features among the various diseases that are characterized by antibody development to epithelial BMZ components, EBA is classified as a pemphigoid variant. Differential diagnoses that should be considered include bullous pemphigoid (BP), cicatricial/mucous membrane pemphigoid (MMP), bullous systemic lupus erythematosus (BSLE), pemphigus vulgaris (PV), linear IgA disease, and porphyria cutanea tarda. Recessive dystrophic epidermolysis bullosa, a rare inherited blistering disorder characterized by the congenital absence of type VII collagen, may also be considered.
EBA has been regarded as the prototypic acquired subepidermal immunobullous disease that demonstrates dermal (floor) BMZ antibody localization with split-skin substrate, also known as salt-split skin, and has two different major types: mechanobullous (classical) and nonmechanobullous (inflammatory). Diagnosis is based on a combination of clinical presentation and laboratory testing, including histopathology, direct immunofluorescence (DIF), and broad epithelial antibody serologic testing.
Quick Answers for Clinicians
There are two major forms of epidermolysis bullosa acquisita (EBA), mechanobullous (classical) and nonmechanobullous (inflammatory). Approximately one-third of patients present with the former, and two-thirds present with the latter. Nonmechanobullous EBA is further divided into four subtypes, with rare case reports of a fifth immunoglobulin M (IgM) type. Patients may present with overlapping symptoms, and presentation may shift over time.
Dermal (floor) localization of IgG antibodies on a split-skin substrate (also known as salt-split skin) by indirect immunofluorescence (IIF) defines four basement membrane zone (BMZ) antibody-associated disease subtypes: epidermolysis bullosa acquisita (EBA), bullous systemic lupus erythematosus (BSLE), anti-p200 (laminin g1) pemphigoid, and anti-laminin-332 pemphigoid. EBA and BSLE are both characterized by antibodies to type VII collagen. Dermal BMZ antibody localization (floor of salt-split skin) has been conventionally linked with the diagnosis of EBA; however, a recent study of serum specimens with dermal IgG antibody reactivity on split-skin substrate revealed that the majority had antibodies directed to p200/laminin g1, whereas considerably smaller subsets demonstrated type VII collagen, laminin-332, and undefined antibodies.
Patients with anti-p200 pemphigoid are typically younger than those with bullous pemphigoid (BP) and have lesions that clinically resemble both BP and the inflammatory EBA variant. An association between psoriasis and anti-p200 pemphigoid has been reported, mainly in men, with more frequent truncal and less mucosal pemphigoid involvement. Mucous membrane involvement is predominant in the anti-laminin-332 pemphigoid variant. Clinical laboratory tests for antibodies to p200 and laminin-332 are not readily available. However, recognition of the association of anti-laminin-332 pemphigoid with underlying or developing malignancy (typically solid tumor) in up to one-third of cases is critical and highlights the importance of differentiating the dermal-predominant pemphigoid subtypes so that an appropriate clinical evaluation is conducted.
Like epidermolysis bullosa acquisita (EBA), bullous systemic lupus erythematosus (BSLE) is regarded as a pemphigoid variant/basement membrane zone (BMZ) antibody-associated disease. Patients with BSLE demonstrate some of the same immunopathologic features present in EBA, including expression of autoantibodies to type VII collagen. BSLE can potentially satisfy diagnostic criteria for EBA. However, patients with BSLE typically present with systemic disease manifestations, including lupus nephritis, and often demonstrate multiple lupus-associated serologic markers, such as antinuclear antibodies and double-stranded DNA (dsDNA) antibodies. Direct immunofluroscence (DIF) testing can help distinguish BSLE from other BMZ antibody-associated diseases by detecting the presence of multiple immunoglobulin classes (eg, IgG, IgM, IgA) and showing granular immune deposits along the BMZ.
Indications for Testing
Laboratory testing for EBA should be considered in patients with skin and mucous membrane disorders who present with skin fragility, blistering, and erosions that result in scarring and milia formation.
Because EBA and the more common BP have similar clinical presentations, histopathology, and immune profiles, EBA should be considered when the initial diagnostic consideration is BP.
For more information about the indications for testing and clinical presentations of various autoimmune bullous diseases, see the Disease-Specific Indications and Features table in the ARUP Consult Immunobullous Diseases topic.
Laboratory Testing
Diagnosis
The diagnosis of EBA is complicated by its varying presentations and the overlap of its clinical and immune profiles with those of other epithelial autoantibody-associated blistering diseases. EBA is one of several diseases that should be suspected in patients presenting with blistering disorders. An effective testing strategy combines DIF on perilesional skin, broad epithelial antibody serologic testing that includes an assessment for type VII collagen antibodies, and formalin-fixed tissue histopathology. Criteria for the diagnosis of EBA have been published and incorporate other tests that may be available only in specialty laboratories. For more information, see Criteria for Diagnosis.
For more information about the use of serology to differentiate among autoimmune bullous diseases, see the Primary Autoantigens Associated With Specific Immunobullous Skin Diseases table in the ARUP Consult Immunobullous Diseases topic and the recent review, Diagnostics for Dermatologic Diseases with Autoantibodies.
Immunopathology
In patients with EBA, DIF on perilesional skin shows linear BMZ antibody reactivity along the epidermal-dermal junction in skin and along the epithelial-subepithelial junction in mucosa. DIF positivity typically includes linear IgG and C3 but may occasionally include IgA or IgM. A perilesional skin specimen should be procured for DIF testing because a lesional biopsy specimen may yield a false-negative result. DIF is the most sensitive diagnostic test for pemphigoid variants, including EBA; however, the various BMZ antibody-associated diseases cannot be definitively characterized on the basis of biopsy alone.
The analysis of the serration patterns that result from DIF on perilesional skin can help differentiate between EBA and other subepithelial autoimmune bullous diseases. In EBA and BSLE, DIF demonstrates a “u-serrated” linear pattern of IgG along the BMZ, as compared to the “n-serrated” pattern in other BMZ antibody-associated bullous diseases. The serration pattern is not recognized in mucosal biopsy specimens and may not be detected in skin specimens.
A modified DIF technique has been described that utilizes BMZ-split perilesional skin or mucosa from patients with suspected EBA or pemphigoid. Ostensibly, this technique allows for more precise localization of antibody binding to the dermal side (floor) and, therefore, provides additional information for diagnosis. However, the technique is infrequently utilized with DIF because of its technical difficulty. In particular, BMZ separation is often difficult near (perilesional) or with affected skin and frequently cannot be performed on mucosal specimens.
Serology
In patients with a compatible clinical presentation, the detection of circulating antibodies against type VII collagen allows for a highly probable diagnosis of EBA, although these antibodies may be increased in BSLE and other autoimmune diseases, including inflammatory bowel disease (IBD). Patients with EBA may not have detectable circulating type VII collagen antibodies in available assays, so a negative test result does not rule out a diagnosis of EBA. Different methodologies may be used to detect type VII collagen antibodies. Specifically, indirect immunofluorescence (IIF) on split-skin substrate and enzyme-linked immunosorbent assay (ELISA) testing for type VII collagen antibodies are often performed for the diagnosis of EBA.
Indirect Immunofluorescence
IIF may be performed with human salt-split skin and monkey or rabbit esophagus substrates to detect type VII collagen antibodies. IIF on salt-split skin has been shown to have a lower sensitivity than either ELISA or immunoblotting (Western blot) and does not specifically identify the antigenic target. IIF on BMZ split-skin substrate (also known as salt-split skin) aids in differentiating between EBA and BP because the BMZ antibodies show reactivity with the dermal side or floor of the separation in EBA and are reactive with the epidermal side or roof in BP. However, BMZ antibodies also show reactivity with the dermal side (floor) of split-skin substrates in anti-laminin-332 pemphigoid and anti-p200/laminin γ1 pemphigoid; thus, these disorders must be ruled out before a diagnosis of EBA can be made. Studies indicate that anti-p200/laminin γ1 pemphigoid is the most common pemphigoid disease in which autoantibodies bind to the dermal floor. IIF can also be performed on type VII collagen-deficient skin substrate as an inverse surrogate for a specific assay.
Recently, cultured cells expressing recombinant epithelial target proteins on chemically activated cover glasses, called Biochips, have been developed as substrates for IIF testing. In particular, IgG antibodies to the noncollagenous 1 domain of type VII collagen (NC1 Col7)-transfected cells can be detected on Biochips, aiding in the diagnosis of EBA. IgG antibodies to laminin-332-transfected cells also can be detected on Biochips. These commercially available tests are sensitive, specific, rapid, and may be a substitute for the respective ELISA.
ELISA
ELISAs are commercially available tests used for the detection of IgG type VII collagen antibodies. These tests have a higher sensitivity for EBA than the other most common methodologies (ie, IIF on salt-split skin and immunoblotting). Type VII collagen is a major component of the anchoring fibrils that attach the epidermis to the underlying dermal connective tissue and is composed of three identical alpha chains, each with a collagenous domain flanked by two noncollagenous (NC) domains, NC1 and NC2. Antibodies are more commonly directed at the NC1 domain; the NC2 domain is a minor antigenic target. ELISA kits are commercially available to test for antibodies directed against the NC1 and NC2 domains, and ELISAs that test both the Col7-NC1 and Col7-NC2 domains have a higher sensitivity than those that only test the Col7-NC1 domain.
ELISAs for type VII collagen antibodies are not entirely specific for EBA and may show increased levels in patients with IBD or other autoimmune bullous diseases.
Immunoblotting
Immunoblotting, or Western blotting, is a methodology that can be used as a substitute for ELISA to detect circulating type VII collagen antibodies. It is used in investigative studies as the diagnostic standard. However, it is less standardized than ELISAs due to limitations in scalability that make it less practical for diagnostic clinical laboratory testing.
Other Immunolocalization Tests
Other tests that provide support for the diagnosis of EBA include the following:
| Test | Description of Characteristic Findings in EBA | Specimen Type |
|---|---|---|
|
Standard transmission EM |
An electron-dense band below the lamina densa of the BMZ in the anchoring fibrils zone and/or cleavage below the lamina densa maintaining attachment to the roof of the blister and/or decreased anchoring fibrils |
Tissue |
|
Direct IEM |
Thick immune deposits in the anchoring fibrils zone with cleavage under the deposits |
Tissue |
|
FOAM |
Immune deposits below the basal keratinocyte membrane, lamina lucida, and lamina densa components on image analysis or confocal microscopy |
Tissue |
|
Indirect IEM |
Immune deposits on the ends of anchoring fibrils |
Serum |
|
EM, electron microscopy; FOAM, fluorescence overlay antigen mapping; IEM, immunoelectron microscopy |
||
Histopathology
Histopathology of lesional skin biopsy specimens may reveal subepidermal blistering (found in pemphigoid disorders such as EBA) and can be used to distinguish EBA from disorders such as pemphigus that show intraepidermal blistering. In the mechanobullous form of EBA, generally very few or no inflammatory infiltrates are detected; in the inflammatory form, neutrophils, eosinophils, monocytes, and lymphocytes are found in the upper dermis. Histopathology cannot be used to differentiate among the various pemphigoid disorders.
Monitoring
Type VII collagen serum antibody levels have been shown to correlate with disease activity in patients with EBA. (3- Vorobyev 2018) Response to treatment can, therefore, be monitored with type VII collagen antibody ELISAs. Additionally, because the antibody reactivity profiles of epithelial components can change over time, monitoring with IIF serum testing can aid in assessing disease expression.
Criteria for Diagnosis
The diagnostic criteria from the International Bullous Disease Group (IBDG) allow for different combinations of findings to establish an EBA diagnosis (although the criteria do not distinguish between EBA and BSLE). These criteria vary depending on differentiating laboratory test findings that support the presentation of a bullous disorder within the clinical spectrum and the availability of tests:
- Scenario 1 (see table): the ideal, with both serum antibodies and differentiating immunologic marker test analyses available
- Scenario 2 (see table): without serum antibodies but with differentiating immunologic tissue marker test analyses
- Scenario 3 (see table): without available testing for defining serum antibodies and without available testing for differentiating immunologic tissue markers
| Criteria | Clinical Scenarios and Combinations of Diagnostic Results | ||||
|---|---|---|---|---|---|
| Assessment | Result | Scenario 1b | Scenario 2 | Scenario 3c | |
|
Clinical assessment |
Bullous disorder within defined clinical spectrum |
✔ |
✔ |
✔ |
|
|
DIF microscopy of perilesional skin or mucous membrane |
Linear IgG and/or IgA, with or without IgM, epithelial BMZ reactivity, and/or linear C3 BMZ localization |
✔ |
✔ |
✔ |
|
|
Histopathology (optional) |
Reveals subepithelial or subepidermal blister with or without inflammation |
✔ |
✔ |
✔ |
|
|
Immunoblot, ELISA |
Detection of serum type VII collagen autoantibodies |
✔d |
|
|
|
|
IIFc |
IIF on collagen VII-deficient skin |
No autoantibodies detected |
✔d | ||
|
Laminin-332 and p200/laminin γ1 antibody assays |
No autoantibodies detected |
✔d | |||
|
Indirect IEM |
Labeling anchoring fibrils |
✔d | |||
|
DIF microscopy pattern analysis |
A “u-serration” linear BMZ pattern |
|
✔d |
|
|
|
Direct IEM of perilesional skin |
Immune reactivity with anchoring fibrils and/or the lamina densa |
|
✔d |
|
|
|
FOAM |
In vivo bound immune deposits below type IV collagen |
|
✔d |
|
|
|
DIF on patient’s salt-split skin and/or IIF on salt-split skin substrate |
Dermal (floor) labeling and exclusion of antibodies against laminin-332 and p200/laminin γ1 |
|
|
✔ |
|
|
aThese criteria do not address the differential diagnosis between EBA and BSLE. bProvides a highly probable EBA diagnosis. cDermal (floor) BMZ antibodies on salt-split skin substrate by IIF; diagnostic confirmation presumed (not definite). dOnly one of these criteria must be met for diagnosis. |
|||||
ARUP Laboratory Tests
Use with serum immunobullous disease/epithelial antibody testing and formalin-fixed tissue histopathology for assessment of pruritic, urticarial, blistering, eczematous, and/or erosive disorders
Use with formalin-fixed tissue histopathology for assessment of inflammatory, immune-mediated cutaneous disease
Optimal specimen location and complementary serum testing and/or histopathology examination vary according to disease type; note that specimen location and transport medium/fixative are different for DIF testing and fixed-tissue histopathology
Direct Immunofluorescence
Use as an initial comprehensive testing panel to aid in diagnosing and distinguishing among skin and mucous membrane disorders that present with blistering, erosions, eczema, pruritus, and/or urticaria
Use to assess suspected epithelial antibody-associated immunobullous diseases, pemphigoid, pemphigus, and their variants that are not clinically distinguishable, have nonspecific features, potentially express overlapping epithelial antibodies, and/or are indicated by concurrent DIF biopsy
Semi-Quantitative Indirect Immunofluorescence (IIF)/Semi-Quantitative Enzyme-Linked Immunosorbent Assay (ELISA)
Components: BMZ antibodies, IgG by IIF; BMZ antibodies, IgA by IIF; BP180 and BP230 antibodies, IgG by ELISA; type VII collagen antibodies, IgG by ELISA; cell surface antibodies, IgG by IIF; desmoglein 1 and 3 antibodies, IgG by ELISA; pemphigus antibodies, IgA by IIF
Use as the preferred initial diagnostic panel for suspected BMZ antibody-associated skin and mucous membrane disorders that present with blistering, erosions, eczema, urticaria, pruritus, and/or mucositis
May be indicated by concurrent DIF biopsy
Alternatively, order the comprehensive Immunobullous Disease Antibody Panel for initial serum diagnostic assessment of epithelial antibody-associated diseases, pemphigoid, pemphigus, and their variants
Semi-Quantitative Indirect Immunofluorescence (IIF)/Semi-Quantitative Enzyme-Linked Immunosorbent Assay (ELISA)
Components: BMZ antibodies, IgG by IIF; BMZ antibodies, IgA by IIF; BP180 and BP230 antibodies, IgG by ELISA; type VII collagen antibodies, IgG by ELISA
Use to monitor disease in patients diagnosed with EBA or BSLE with increased IgG type VII collagen antibody levels
For initial diagnosis, including discrimination among various immunobullous diseases, and assessment of disease progression/changes and intermittent monitoring, the Immunobullous Disease Antibody Panel or Basement Membrane Zone Antibody Panel is preferred
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Use to assess and monitor pemphigoid, pemphigoid variants, and linear IgA disease and to discriminate among the immunobullous diseases with epithelial BMZ antibodies
May be indicated by concurrent DIF biopsy; the preferred initial diagnostic serum panel is Basement Membrane Zone Antibody Panel
Semi-Quantitative Indirect Immunofluorescence (IIF)/Semi-Quantitative Enzyme-Linked Immunosorbent Assay (ELISA)
Components: BMZ antibodies, IgG by IIF; BMZ antibodies, IgA by IIF; BP180 and BP230 antibodies, IgG by ELISA
Use to monitor linear IgG and IgA BMZ antibody-associated diseases and IgG and IgA cell surface antibody-associated diseases in which antibody levels by ELISAs may not be increased and/or to assess for changing patterns of epithelial antibody expression
May be used as a general initial serum test for immunobullous diseases; however, for more sensitive and specific serum testing for pemphigoid, EBA, or IgG variant pemphigus, refer to Basement Membrane Zone Antibody Panel or Pemphigus Antibody Panel, IgG
Semi-Quantitative Indirect Immunofluorescence (IIF)
Components: BMZ antibodies, IgG by IIF; BMZ antibodies, IgA by IIF; cell surface antibodies, IgG by IIF; pemphigus antibodies, IgA by IIF
Use to assess and monitor IgG BMZ antibodies in patients with pemphigoid, pemphigoid variants/subtypes, and EBA, especially those with normal relevant IgG BP180, IgG BP230, and IgG type VII collagen antibody levels by ELISAs
Testing should be correlated with concurrent DIF biopsy
For initial pemphigoid or EBA diagnosis, a more comprehensive serum panel is preferred; refer to Immunobullous Disease Antibody Panel
Semi-Quantitative Indirect Immunofluorescence (IIF)
Use to assess and monitor IgA BMZ antibodies in patients with linear IgA disease and variants, including linear IgA bullous dermatosis, chronic bullous disease of childhood, linear IgA/IgG bullous dermatosis, and IgA-variant EBA
Testing should be correlated with concurrent DIF biopsy
For initial pemphigoid or EBA diagnosis, a more comprehensive serum panel is preferred; refer to Immunobullous Disease Antibody Panel
Semi-Quantitative Indirect Immunofluorescence (IIF)
References
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Prost-Squarcioni C, Caux F, Schmidt E, et al. International Bullous Diseases Group: consensus on diagnostic criteria for epidermolysis bullosa acquisita. Br J Dermatol. 2018;179(1):30-41.
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Chen M, Kim GH, Prakash L, et al. Epidermolysis bullosa acquisita: autoimmunity to anchoring fibril collagen. Autoimmunity. 2012;45(1):91-101.
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Vorobyev A, Ludwig RJ, Schmidt E. Clinical features and diagnosis of epidermolysis bullosa acquisita. Expert Rev Clin Immunol. 2017;13(2):157-169.
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Schmidt T, Hoch M, Lotfi Jad SS, et al. Serological diagnostics in the detection of IgG autoantibodies against human collagen VII in epidermolysis bullosa acquisita: a multicentre analysis. Br J Dermatol. 2017;177(6):1683-1692.
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Omland SH, Gniadecki, R. IgM-type epidermolysis bullosa acquisita. Br J Dermatol. 2015;173(6):1566-1568.
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Suchniak JM, Diaz LA, Lin MS, et al. IgM-mediated epidermolysis bullosa acquisita. Arch Dermatol. 2002;138(10):1385-1386.
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Lau I, Goletz S, Holtsche MM, et al. Anti-p200 pemphigoid is the most common pemphigoid disease with serum antibodies against the dermal side by indirect immunofluorescence microscopy on human salt-split skin. J Am Acad Dermatol. 2019;81(5):1195-1197.
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Xie YH, Wang SH, Li SZ, et al. Coexistence of anti-p200 pemphigoid and psoriasis: a systematic review. Front Immunol. 2022;13:839094.
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Leiferman KM, Snook JP, Khalighi MA, et al. Diagnostics for dermatologic diseases with autoantibodies. J Appl Lab Med. 2022;7(1):165-196.
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Kridin K, Kneiber D, Kowalski EH, et al. Epidermolysis bullosa acquisita: a comprehensive review. Autoimmun Rev. 2019;18(8):786-795.
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Komorowski L, Müller R, Vorobyev A, et al. Sensitive and specific assays for routine serological diagnosis of epidermolysis bullosa acquisita. J Am Acad Dermatol. 2013;68(3):e89-e95.
Additional detail about the tests below and other information useful in assessing EBA and other immunobullous diseases can be found in the ARUP Immunobullous Disease Testing Comparison table.