Bullous disorders with multiple, pathologic autoantibodies include not only PNP* (1) but also pemphigus+pemphigoid (2,3), pemphigus+myasthenia (4) and others. To study such disorders, we need to distinguish common physiologic autoantibodies, which may result from tissue damage, from rare pathologic autoantibodies that cause tissue damage. The latter may bind to normal tissue components in vivo, in patients' skin, in passive transfers (5) and in tissue culture while physiologic autoantibodies bind only to altered tissue components. While single serum tests may fail to distinguish the two, direct IF plus selected combinations of serum tests can usually distinguish the following four main groups of pathologic skin and muscle autoantibodies:

Autoantibody groups	Test methods	Diseases**: antibody groups)** (These are examples)
1) Intercellular and Dsgl/3 antibodies(ab) -> IIF*- esophagus (IgG4) & ELISA* 2) Plakin antibodies -> IB*, IP*, CIIF* 3) Basement membrane zone (BMZ) ab.* -> IIF - esophagus & split skin 4) Muscle striation ab. & acetylcholine receptor ab -> IIF- esophagus & ELISA		PNP*: 1) + 2) also 3) &/or 4)
		Pemphigus + pemphigoid: 1) + 3)
		Pemphigus + myasthenia gravis &/or thymoma: 1) + 4)
		Pemphigus: 1) only
		Pemphigoid or EBA: 3) only
		Erythema multiforme major (6) : 2 ) only

* Abbreviations: CIIF = complement IIF IF = immunofluorescence IIF = indirect IF EBA = epidermolysis bullosa acquisita ELISA = enzyme linked immuno sorbent assay EM = erythema multiforme IB = immunoblot

IP = immunoprecipitation ab = antibodies Dsgl/3 = desmoglein 1 and desmoglein 3 antibodies PNP = paraneoplastic pemphigus BMZ = basement membrane zone MG = myasthenia gravis

** Bullous LE and ANA related bullous disorders merit separate consideration.

1) Pathogenic pemphigus antibodies can now be identified reliably by the combined use of direct IF, routine IgG-IIF on esophagus sections (5), ELISA for Dsgl/3 (7) and the more specific IgG4 direct IF and IIF test; they distinguish true pemphigus reactions from biologic false positive direct IF IgG1 antibodies to Dsgl/3 or other non-pathogenic cell surface antibodies (8). Also, since negative direct IF reactions may be due to focal, transient in vivo binding of pathogenic pemphigus antibodies and since routine IIF and Dsgl/3 ELISA assays may give false positives, IgG4-IIF studies are indicated. Positive IgG4-IIF tests for cell surface reactions appear to be diagnostic of all pemphigus and pemphigus+pemphigoid as well as most PNP cases (3,8,11).

2) Pathogenic plakin antibody detection poses problems because of the limited availability of IP tests. Joly (9) recommends IB tests (10); but positive ID* and IP* reactions with sera of PNP* occur in cases that take a benign course. In the experience of this laboratory CIIF tests on esophagus sections for desmosome-like structures afford sensitive and specific tests for fatal PNP cases (11). Sera of cases with clinical signs of PNP (1) and/or EM major (6) can be tested for plakin antibodies by IB and CIIF as well as for Dsg1/3 by ELISA*, IIF* tests and direct IF methods.

3) Pathogenic basement membrane zone (BMZ) antibodies can be detected reliably by direct IF and routine serum tests by IIF on monkey esophagus (6) or human, salt split normal skin sections (12). These BMZ antibodies are diagnostic of bullous or cicatricial pemphigoid, EBA* and less common autoantibodies to the BMZ such as those of epiligrin autoimmunity (EA). (See also UPDATE for methods of distinction of pemphigoid from EBA or EA). ELISA, IB and IP methods have, thus far, been primarily of academic value.

4) Muscle stria autoantibodies are markers for more pathogenic motor endplate autoantibodies that cause muscle paralysis of myasthenia gravis (MG) (4,5). Although the muscle antibodies themselves, which are detected on skeletal muscle of the upper half of monkey esophagus by routine IIF tests, have limited pathogenicity, many cases with elevated titers have thymomas and/or coexisting antibodies of MG. Failures to carry out checks for antibodies of MG in patients with muscle stria antibodies can be fatal (11,13). These potential risks merit rapid checking particularly in cases with coexistence of MG with pemphigus or PNP. Two steps are indicated: a) Sera with muscle stria antibodies should be sent to the Neuroimmunology Laboratory of the Mayo Clinic for special studies {X}. b) Positive findings merit an immediate neurology consult.

References
1. Anhalt GJ, Kim S, Stanley JR, Korman N7, Jabs DA, Kory M, Izumi H, Ratrie H, Mutasim D, Ariss-Abdo I" Labib RS. Paraneoplastic pemphigus. An autoimmune mucocutaneous disease associated with neoplasia. N. Engl J Med 1990;323:729-35.
2. Chorzelski TP, Maciejowski E, Jablonska S, DeMento FJ, Grover RW, Holubar K, Beutner EH Coexistence of pemphigus and bullous pemphigoid. Arch Dermatol 1974, 109:849-53.
3. Sami N, Bhol K, Beutner EH, Plunkett RW, Leiferman KM, Ahmed AR. Serologic features of pemphigus vulgaris in bullous pemphigoid patients. Clin Immunol (submitted 2001).
4. Beutner EH, Chorzelski TP, Hale WL, Hausmanowa-Petrusewicz I. Autoimmunity in concurrent myasthenia gravis and pemphigus erythematosus. J Am Med Assoc 1968,203:845-49.
5. Beutner EH, Lever WF, Witebsky E, Jordon RE, Chertock B. Autoantibodies in pemphigus vulgaris. Responses to an intercellular substance of epidermis. J Am Med Assoc 1965;192:682-8.
6. Foedinger D, Sterniczky B, Elbe A, Anhalt G, et al. Autoantibodies against Desmoplakin I and 21 define a subset of patients with erythema multiforme major. J Invest Dermatol 1996;106:1012-16. 7. Amagai M, Nishikawa T, Nousari HC, Anhalt GJ, Hashimoto T. Antibodies against desmoglein 3 (pemphigus vulgaris antigen) are present in sera from patients with paraneoplastic pemphigus and cause acantholysis in vivo in neonatal mice. J Clin Invest 1998;102:775-82.
8. Bhol R, Nataraja R, Nagarwalla N, Mohimen A, Aoki V, Ahmed AR. Correlation of peptide specificity and IgG subclasses with pathogenic and nonpathogenic autoantibodies in pemphiqus vulgaris. Proc Nat Acd Sci USA 1995,92:5239-43.
9. Joly P, Richard C, Gilbert D, Courville P, Chosidow 0, Roujeau JC, Beylot-Barry M, D'Incan M, Martle Ph, Lauret Ph, Tron F, and the members of the French Study Group on Bullous Diseases. Sensitivity and specificity of clinical, histologic, and immunologic features in the diagnosis of paraneoplastic pemphigus. J Am Acad Dermatol 2000;43:619-26.
10. Hashimoto T, Amagai M, Wantanabe K, Chorzelski TP, Bhogal BS, Black MM, Stevens HP, Boorsma DM, Korman NJ, Gamou S, Shimizu N, Nishikawa T. Characterization of paraneoplastic pemphigus autoantigens by immunoblot analysis. J Invest Dermatol 1995;104:829-34.
11. Helm TN, Beutner EH, Kulick KB, Korman NJ, Plunkett RW. Complement fixing immunofluorescence findings may correlate with clinical outcome in patients with paraneoplastic pemphigus. J Am Acd Dermatol (in press 2001).
12. Gammon WR, Kowalewski C. Chorzelski TP, Kumar V, Briggaman RA, Beutner :H. L etc immunofluorescence studies of sodium chloride separated skin in the differential diagnosis or bullous pemphigoid and epidermolysis bullosa acquisita. J Am Acad Dermatol 1990,22:664-70.
13. Beutner EH, Leff IL, Fazekas G, Witebsky E. Immunologic studies of two cases of fatal myasthenia gravis. J Am Med Assoc 1965,191:461-65.

{X} Call Dr. Vanda Lennon, Neuroimmunology Laboratory, Mayo Clinic 507 284 8726 * See Foot note of table.

Copyright © 2001 Beutner Labs, Inc.
Published with permission.