Diagnostic tests 1. Skin and mucosal biopsy studies by direct immunofluorescence detect IgG in the basement membrane zone (BMZ) in about 90% of cases of bullous pemphigoid (BP), epidermolysis bullosa acquisita (EBA) and related autoimmune disorders. 2. Blood tests for autoantibodies by indirect immunofluorescence on esophagus sections and on unsplit and 1 M NaCl split skin detect BMZ antibodies in about 70% of BP cases, including some that are negative by direct immunofluorescence, about 50% of EBA cases and a lower percentage of cases with related autoimmune disorders. 3. Selected laboratory methods can distinguish BP from EBA, if needed. If differentiation is indicated, the selection of methods depends on the specimens and the type of autoimmune BMZ reaction they give.

Specimen to collect:

Focus of UPDATE: This UPDATE focuses on the differentiation of EBA from BP and related forms of pemphigoid and their clinical relevance. Biopsy findings of BMZ deposits of IgG, the C3 complement component (C3), as well as IgA and IgM, in some cases, plus blood tests for BMZ autoantibodies characterize both EBA and BP and related forms of pemphigoid*. These disorders require treatment which differs from that of similar eruptions with other etiologies. Combined clinical and laboratory studies can distinguish these reliably (1,2). See UPDATE on "Mucosal lesions with subepithelial immunofluorescent markers" for data on cicatricial pemphigoid and other mucosal disorders that can be distinguished by direct IF and other immunopathologic studies.

		DIAGNOSTIC METHODS
Bullous, vesicular and related disorders**	Types of lesions	Biopsy studies
		H&E, light microscopy	Direct IF*	Indirect IF* for anti-BMZ antibodies
Bullous pemphigoid Urticarial and other forms of pemphigoid	Skin and mucosal Skin	Subepidermal bulla Eosinophilic infiltrate	IgG and C3 in BMZ IgG and C3 in BMZ	70-80% pos. 50% or less pos.
Epidermolysis bullosa acquisita & bullous LE	Skin and mucosal	Subepidermal bulla	IgG, C3 plus IgA &/or IgM	~50% pos.

* Indirect IF = immunofluorescence with serum from ctotted blood sample for BMZ
** See UPDATE - Pemphigoid & related autoimmune diseases: Diagnosis with biopsy and serum studies.

Pathologic roles of autoimmunity in BP and EBA and their antigens Since BP and related forms of pemphigoid as well as EBA are caused by pathologic autoantibodies to specific antigens in the BMZ, their diagnosis requires the detection of these BMZ antibodies. The autoantibodies of BP and EBA are directed to different antigens but the methods listed in the above Table do not distinguish between them clearly. The antigens of BP are hemidesmosome components of the basal cells and appear in the upper lamina lucida, ultrastructurally. They include glycoproteins of 230 kD and 180 kD (4). Antibodies to these BP antigens produce lesions in the lamina lucida. The EBA autoantibodies to type VII collagen are located in anchoring fibrils ultrastructurally. They induce lesion formation below the lamina densa (5,6).

Methods of differentiating BP or other forms of pemphigoid from EBA and bulllous LE If clinical findings point to the need to rule out EBA in a case with BMZ reactions, one of three types of studies can aid in differentiating EBA from BP, under most conditions***, notably: 1) Direct IF Of a "salt: split patient biopsy" reveals IgG in the BMZ of the roof of split in BP and of the floor of the split in EBA, if the unsplit specimen is of normal skin or mucosa with IgG in the BMZ. 2) Since laminin and type IV Collagen antibodies (produced in rabbits) react with the lamina densa part of the BMZ, tests with these reagents on biopsies with fresh vesicles yield reactions in the BMZ of the floor of vesicles in BP and in the roof of vesicles in EBA if fresh vesicles are present in the specimen. The BP antibodies produce vesicles in the lamina lucida and the EBA antibodies produce vesicles below the lamina densa. 3) Indirect IF tests of the patient's serum on "salt split" normal skin reveals the same distribution of BMZ reaction in BP and EBA if the serum has antibodies that react with the BMZ of the split skin. A variant of this test will be a serum test: with a BP2 ELISA method (7).

*** For added information on methods of differentiation, see UPDATE - Differentiation of bullous pemphigoid (BP) from epidermolysis bullosa acquisita (EBA) and other forms of BMZ autoimmunity.

References:
1. Beutner EH, Chorzelski TP, Jordon RE. Autosensitization in pemphigus and pemphigoid. Charles Thomas. Springfield IL, 1970.
2. Gammon WR, Briggaman RA, Inman A0, Queen LL, Wheeler CE. Differentiating anti-lamina lucida and anti-sublamina densa anti-BMZ antibodies by indirect immunofluorescence on 1.0 M/L sodium chloride separated skin. J Invest Dermatol 82:139-144,1984.
3. Weigand DA. Effect of anatomic region on immunofluorescence diagnosis of bullous pemphigoid. J Am Acd Dermatol 12:274-278,1985.
4. Stanley JRP, Hawley-Nelson SH, Yuspa EF, Shevach EM, Katz SI. Characterization of bullous pemphigoid antigen: A unique basement membrane protein of stratified squamous epithelia. Cell 24:897-903,1981.
5. Gao, SQ, Bystryn JC. Identification of a novel basement membrane antigen (p84) defined by sera with antibodies to both the epidermal and dermal side of split= skin. J Invest Dermatol 102:236-240,1994.
6. Gammon WR, Briggaman RA, Woodley DT, Heald PW, Wheeler CE. Epidermolysis bullosa acquisita: A pemphigoid-like disease. J Am Acad Dermatol 11:820-832,1984. 7. Zillikens D. Acquired skin disease of the hemidesmosomes. J Dermatol Sci 20: 134-54,1999.

Copyright © 1999 Beutner Labs, Inc.
Published with permission.