Background

This rare disorder is also known as 105kd bullous dermatosis because the target antigen of the autoantibodies is directed against a 105 kd protein. It is a non-scarring subepidermal bullous dermatosis occurring on the skin and mucous membranes. Clinically it resembles toxic epidermal necrolysis or pemphigus vulgaris.

This subepidermal blister is associated with neutrophils within the subepidermal papillae, resembling dermatitis herpetiformis. Direct immunofluorescence reveals linear staining for IgA and C3 along the dermoepidermal junction, localized in the lower lamina lucida.

OUTLINE

Epidemiology
Pathogenesis
Histopathological Features and Variants
Special Stains/Immunohistochemistry/Electron Microscopy
Differential Diagnosis
Commonly Used Terms

EPIDEMIOLOGY	CHARACTERIZATION
SYNONYMS	anti-105kd bullous dermatosis
INCIDENCE	Rare

 

PATHOGENESIS	CHARACTERIZATION
Defective in vivo expression and apparently normal in vitro expression of a newly identified 105-kDa lower lamina lucida protein in dystrophic epidermolysis bullosa. Chan LS, Fine JD, Hammerberg C, Bauer EA, Cooper KD. Department of Dermatology, University of Michigan School of Medicine, Ann Arbor, USA.	Br J Dermatol 1995 May;132(5):725-9 Abstract quote We have previously identified a novel 105-kDa lower lamina lucida protein detected by the autoantibodies from a group of patients who developed a unique immune-mediated subepidermal bullous dermatosis. We sought to determine if this novel basement membrane zone (BMZ) protein is normally expressed in the skin of patients with various subsets of epidermolysis bullosa (EB). Indirect immunofluorescence microscopy performed on non-lesional skin sections from patients with three major EB subsets revealed absence or significantly reduced expression of this novel BMZ protein in 20 out of 23 skin sections from patients with generalized dominant and recessive dystrophic EB. However, immunoblot analyses with the autoantibodies on Western-blotted proteins revealed that a comigrating 105-kDa protein is present in both cytosol extracts (n = 6) and conditioned media (n = 3) of cultured dermal fibroblasts derived from patients with dystrophic EB, as well as those cultured from two healthy individuals. Although the reason for such disparate findings is not known, the defective in vivo expression of this novel 105-kDa protein in dystrophic EB is presumably not due to a failure of fibroblasts to synthesize or secrete the protein. It is possible, however, that the 105-kDa protein may be unable to incorporate into the BMZ because it is produced in a dysfunctional form, or its BMZ binding site is missing. It is also possible that other structural alterations in skin BMZ, which occur in dystrophic EB, result in masking of the antigenic binding by the autoantibody when intact BMZ is probed.
A newly identified 105-kD lower lamina lucida autoantigen is an acidic protein distinct from the 105-kD gamma 2 chain of laminin-5. Chan LS, Wang XS, Lapiere JC, Marinkovich MP, Jones JC, Woodley DT. Department of Dermatology, Northwestern University Medical School, Chicago, Illinois 60611-3010, USA.	J Invest Dermatol 1995 Jul;105(1):75-9 Abstract quote A 105-kD lower lamina lucida antigen (p105) has been detected by autoantibodies (anti-p105) from patients with a novel immunobullous disease. To distinguish p105 from other known lamina lucida components, we performed comparative immunoblotting on purified human amniotic laminin-5 (kalinin), 804G matrix (enriched in laminin-5), and keratinocyte and fibroblast proteins using anti-804G matrix antibody (J-18) and anti-p105. J-18 labeled the truncated laminin-5 gamma 2 chain in amniotic laminin-5, 804G matrix, and keratinocyte conditioned medium, but did not label fibroblast cytosol. Conversely, anti-p105 did not label amniotic laminin-5 or 804G matrix, but did label p105 in both keratinocyte conditioned medium and fibroblast cytosol. J-18 labeled the 105-kD laminin-5 gamma 2 chain in reduced keratinocyte proteins and a 400-kD laminin-5 complex under non-reducing conditions. In contrast, anti-p105 labeled p105 under both reducing and non-reducing conditions but did not label a 400-kD protein complex. Similarly, comparative immunoblotting on keratinocyte proteins using anti-p105 and anti-laminin-1 revealed no commonly labeled protein bands. Electrophoretic fractionations by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting of these fractions revealed that the peak fractions of keratinocyte proteins reactive with anti-p105 are different from those reactive with J-18. Furthermore, keratinocyte proteins fractionated by Mono Q anion-exchange chromatography revealed fractions immunoreactive with anti-p105, whereas J-18 showed no reactivity with these fractions. Two-dimensional gel electrophoresis and immunoblotting with anti-p105 revealed p105 to be an acidic protein with isoelectric points between 5.7 and 6.3, distinct from the isoelectric points of laminin-5 gamma 2 chain. We conclude that p105 is an acidic protein located in the lamina lucida and distinct from the truncated laminin-5 gamma 2 chain and the laminin-1 family.
The 105-kDa basement membrane autoantigen p105 is N-terminally homologous to a tumor-associated antigen. Chan LS, Woodley DT. Immunodermatology Division, Department of Dermatology, Northwestern University Medical School, Chicago, Illinois 60611, U.S.A.	J Invest Dermatol 1996 Aug;107(2):209-14 Abstract quote Certain constitutive skin basement membrane components, such as bullous pemphigoid antigens and epidermolysis bullosa acquisita antigen, were discovered because they were targeted by an autoimmune reaction. We aimed to purify and characterize a 105-kDa skin basement membrane protein termed p105 recognized by autoantibodies (anti-p105) from patients with a unique immune-mediated subepidermal blistering skin disease. A simian virus 40-transformed human fibroblast cell line that synthesizes and secretes p105 was utilized as the protein source. p105 was partially purified by salt-gradient fractionation of serum-free conditioned medium through a Mono Q anion-exchange column and by examining each fraction with protein staining and immunoblotting against anti-p105. p105 was isolated from polyacrylamide gel electrophoresis gels, blotted onto polyvinylidene difluoride membrane, and subjected to protein microsequencing. The 20 microsequenced N-terminal amino acids exhibited no homology to known basement membrane proteins but exhibited a 70% homology to a 90-kDa tumor-associated antigen. Antibodies raised against a peptide generated from these amino acid sequences reacted to a 105-kDa western-blotted keratinocyte and fibroblast protein and a basement membrane component. p105 resisted digestion by glycosidases chondroitinase ABC, neuraminidase, and N-glycosidase F but was cleaved by protease V8 to antigenic fragments of 22 kDa and 14 kDa. The synthesis of p105 was inhibited by cycloheximide. We conclude that p105 is a unique basement membrane component produced by both keratinocytes and fibroblasts.

 

HISTOLOGICAL TYPES	CHARACTERIZATION
GENERAL
A novel immune-mediated subepidermal bullous dermatosis characterized by IgG autoantibodies to a lower lamina lucida component. Chan LS, Cooper KD. Department of Dermatology, University of Michigan School of Medicine, Ann Arbor.	Arch Dermatol 1994 Mar;130(3):343-7 Abstract quote BACKGROUND: Immune-mediated subepidermal bullous dermatoses characterized by in vivo-bound linear IgG deposition at the cutaneous basement membrane zone include bullous pemphigoid, ocular cicatricial pemphigoid, anti-bullous pemphigoid antigen mucosal pemphigoid, anti-epiligrim mucosal pemphigoid, epidermolysis bullosa acquisita, and the bullous eruption of systemic lupus erythematosus. In this article, we describe a novel IgG-mediated bullous dermatosis. OBSERVATIONS: Clinically, a unique nonscarring dermatosis was characterized by the sudden onset of extensive bullae and erosions on mucous membrane and skin, resembling toxic epidermal necrolysis or pemphigus vulgaris. Histologically, the patient's skin lesion demonstrated neutrophilic papillary dermal infiltration and subepidermal blister formation, resembling dermatitis herpetiformis. Immunopathologically, there was linear IgG and C3 deposition at the skin basement membrane zone. The patient responded well to prednisone and azathioprine immunosuppression and has achieved a lasting remission without further therapy. Further immunologic investigations revealed that this unique dermatosis is distinct from all other known IgG-mediated subepidermal bullous dermatoses. CONCLUSIONS: This novel deep lamina lucida pemphigoid can be distinctly termed anti-p105 pemphigoid on the basis of antigenic specificity of the autoantibodies. Although this novel dermatosis resembles toxic epidermal necrolysis clinically, prudent use of diagnostic immunofluorescence studies can clearly delineate its immunologic nature. Prompt recognition of this unique dermatosis and timely initiation of appropriate immunosuppressive therapy could be life-saving for those patients suffering from this dermatosis

 

SPECIAL STAINS/IMMUNOPEROXIDASE/ OTHER	CHARACTERIZATION
DIRECT IMMUNOFLUORESCENCE
Identification and partial characterization of a novel 105-kDalton lower lamina lucida autoantigen associated with a novel immune-mediated subepidermal blistering disease. Chan LS, Fine JD, Briggaman RA, Woodley DT, Hammerberg C, Drugge RJ, Cooper KD. Department of Dermatology, University of Michigan School of Medicine, Ann Arbor.	J Invest Dermatol 1993 Sep;101(3):262-7 Abstract quote Certain skin basement membrane components, such as bullous pemphigoid antigens and epidermolysis bullosa acquisita antigen, were discovered as a result of an autoimmune reaction. In this report, we describe a unique lamina lucida determinant associated with a novel immune-mediated subepidermal bullous dermatosis. This unique bullous dermatosis resembled severe toxic epidermal necrolysis clinically. The histologic findings resemble dermatitis herpetiformis. Direct immunofluorescence microscopy detected linear immunoglobulin G (IgG) and C3 deposition at the cutaneous basement membrane zone of lesional and perilesional skin. Direct and indirect immunoelectron microscopy localized the IgG deposits to the lowest portion of the lamina lucida. The patient's autoantibodies, belonging to the IgG1 subclass, labeled basement membrane zone of normal intact human skin, oral mucosa, and conjunctiva, and localized to the dermal side of salt-split normal adult and neonatal human skin, but failed to react with human fetal skin up to 142 gestational days. The patient's autoantibodies failed to react with bullous pemphigoid antigens or epidermolysis bullosa acquisita antigen (type VII collagen) by immunoblotting. Instead, the patient's autoantibodies unequivocally labeled a 105-kilodalton (kD) protein in cellular extracts and conditioned media of human cultured keratinocytes and dermal fibroblasts. The titer of the patient's antibody against the cutaneous basement membrane zone and the intensity of the antibody reactivity against the 105-kD protein paralleled the patient's disease activity. Thus, this 105-kD lower lamina lucida protein represents a novel autoantigen and this patient's disease represents a novel autoantigen and this patient's disease represents a deep lamina lucida pemphigoid, distinguishable from all other known autoimmune bullous dermatoses.
A novel 105-kDa lamina lucida autoantigen: association with bullous pemphigoid. Cotell SL, Lapiere JC, Chen JD, Iwasaki T, Krusinski PA, Chan LS, Woodley DT. Department of Dermatology, Northwestern University School of Medicine, Chicago, Illinois 60611.	J Invest Dermatol 1994 Jul;103(1):78-83 Abstract quote Several cases have been reported of patients with immunemediated subepidermal blistering disorders whose autoantibodies react to antigens present on both the dermal and epidermal side of 1 M NaCl-split skin. In this report, we identify, localize, and characterize the basement membrane zone antigen corresponding to the dermal staining in a patient whose serum stains both the dermal and epidermal side of 1 M NaCl-split skin. This patient's serum contains autoantibodies directed against a 105-kilodalton(kDa) dermal antigen and the 230-kDa epidermal (bullous pemphigoid) antigen. This novel 105-kDa protein was previously identified as the sole antigen in another patient with a unique bullous disease whose autoantibodies were directed against only the dermal side of 1 M NaCl-split skin. This 105-kDa antigen was identical by one- and two-dimensional immunoblot analysis in these two patients. By immunoblot analysis, autoantibodies from our patient labeled a 105-kDa protein within various extracts of human skin basement membrane. Immunoblot analyses using epitope-selected autoantibodies directed against the 105-kDa protein demonstrated that this antigen is independent and distinct from other known basement membrane antigens. The 105-kDa antigen is an extracellular matrix component of the basement membrane, which is synthesized and secreted by both keratinocytes and fibroblasts. Identical electrophoretic migration of cellular and secreted forms of the protein suggested there is no major post-translational modification of the protein. Immunomapping of normal human skin fractured through the dermal-epidermal junction by incubation in 1 M NaCl or by suction blistering demonstrated that the location of the 105-kDa antigen within the basement membrane zone is between the bullous pemphigoid antigens and two other lamina lucida components, laminin and nicein. These data demonstrate clearly that a subepidermal autoimmune bullous disease may have autoantibodies directed against two distinct components of the dermal-epidermal junction.

 

DIFFERENTIAL DIAGNOSIS	KEY DIFFERENTIATING FEATURES
Bullous pemphigoid
Epidermolysis bullosa acquisita

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Salt split skin assay-Normal skin incubated with 1M NaCl which separates the epidermis from dermis. The epidermal half contains the upper lamina lucida, hemidesmosomes, and BP antigen. The dermal half contains laminin 5, lamina densa, and anchoring fibrils.