Linear IgA disease (LAD) is an acquired autoimmune subepidermal bullous disease characterized by the linear deposition of IgA at the basement membrane zone. A minority of cases are induced by drugs, of which the most frequently implicated is vancomycin. The target antigens in idiopathic LAD are heterogeneous, but have not previously been reported in vancomycin-induced LAD. We report three cases, and in two of these we investigated the target antigens. In both we identified IgA antibodies to LAD285 and IgA and IgG antibodies (dual response) to BP180.

Linear IgA disease (LAD) has circulating IgA auto-antibodies which have been found to be associated with epidermal- and dermal-derived antigens. The localization and molecular weight(s) of the IgA target antigen(s) implicated in LAD and their relationship to the target antigens for the IgA antibodies in bullous pemphigoid (BP) and cicatricial pemphigoid (CP) are unknown. Sera from patients with all 3 diseases who had circulating IgA antibodies were studied by immunoblotting with both epidermal and dermal extracts. Our findings indicate that there is heterogeneity in the localization and molecular weights of the target antigen(s), with multiple bands demonstrated with some sera. Three principal target antigens were identified with molecular weights of 110–120, 160–180 and one approximately 285 kD. These antigens were common to all 3 diseases and were found in 25 patients. These results suggest that the target antigens for IgA basement membrane zone antibodies in LAD, BP and CP are multiple, complex in composition and may differ from the conventional BP antigens.

Linear IgA disease (LAD) is characterized by circulating and tissue-bound IgA antibodies against heterogeneous antigens in the cutaneous basement membrane zone. In most cases the cause is unknown, but a minority of cases has been drug induced. We report a 76-year-old man who developed an acute blistering eruption following high-dose penicillin treatment for pneumococcal septicaemia. Indirect immunofluorescence demonstrated dermal binding IgA antibodies, and Western blotting of serum showed reactivity with a 250 kDa dermal antigen corresponding to collagen VII of anchoring fibrils. Indirect immunoelectron microscopy showed antibody labelling in the lamina densa and sublamina densa zone. This is one of the few cases of drug-induced LAD in which the target antigen profile has been characterized, and the first in which the antigen has been shown to correspond to collagen VII.

The objective of this study was to investigate whether circulating basement membrane zone (BMZ) antibodies are present in erosive lichen planus (LP) of the vulva. In total, 56 consecutive women with biopsy-confirmed erosive LP of the vulva were recruited from a vulval clinic in a district general hospital and teaching hospital in Oxfordshire. Indirect immunofluorescence (IgG and IgA) was performed on 56 sera, and 15 were tested to IgG subclasses (1-4). Immunoblotting was carried out on salt-split and urea-extracted epidermal skin extracts on 11. The main outcome measure was the presence or absence of staining at the BMZ. Of the 56 sera, 34 (61%) had weak (neat or 1 : 5) epidermal-binding BMZ antibodies (25 had IgG, 5 had IgA, 4 had both IgG and IgA). All 15 sera tested to IgG showed epidermal binding to one or more IgG subclasses: IgG1 (7 sera), IgG2 (7), IgG3 (7) and IgG4 (0). Immunoblotting identified IgG antibodies to bullous pemphigoid (BP)180 (10/11) and BP230 (2/11). The majority (61%) of patients with vulval erosive LP had circulating serum IgG BMZ antibodies, chiefly reacting with BP180. There was subclass restriction of the IgG response to IgG1, 2 and 3. The significance of these antibodies is uncertain, but they may be a marker for the disease.

Summary Blistering in systemic lupus erythematosus has been divided into three groups.1 A specific subgroup of ‘bullous systemic lupus erythematosus’ has been defined by Gammon et al. on the basis of a number of criteria.2 From our experience of seven patients with bullous systemic lupus erythematosus, and after reviewing the literature, we suggest that the current classification is too narrow. Our patients displayed clinical and immunohistolegical (based on direct and indirect immunofluorescence and Western immunoblotting) heterogeneity. Sera from two patients bound to epidermal epitopes in sodium chloride‐split skin, but immunoblotting was negative. In neither of these patients could the target antigen be type VII collagen, the only antigen identified as pathogenic in this disease. Patients with epidermal binding should not be excluded from a diagnosis of bullous systemic lupus erythematosus. SLE is a disease in which there is a genetic predisposition to form antibodies to type VTI collagen, along with other autoantibodies, many of which may be implicated in blistering. We suggest that the criteria for the diagnosis of BSLE should be revised. We define this disease as an acquired subepidermal blistering disease in a patient with SLE, in which immune reactants are present at the basement membrane zone on either direct or indirect immunofluorescence.

Linear IgA disease (LAD) of adults and children is a dapsone-responsive, autoimmune subepidermal blistering disease characterized by linear IgA deposits at the basement membrane zone (BMZ) of the skin and mucosa. Circulating IgA antibodies to BMZ components are often present. In this study we investigated the ultrastructural localization of the antigens and autoantibodies in six patients with LAD (five adults and one child). Using a direct postembedding immunogold electron microscopy (EM) technique, three different patterns of IgA antibody deposition were seen in the skin of four patients with LAD. The IgA deposits localized within the uppermost part of the lamina lucida and to the basal surface of the hemidesmosome in two patients, to the lamina lucida in one, and to the lamina densa in the fourth patient. Using an indirect immunogold EM technique and serum or purified blister fluid from two additional LAD patients, we showed that the serum autoantibodies of one patient bound to the hemidesmosome of the BMZ, while the autoantibodies in the blister fluid of the other patient bound to the lamina densa and sublamina densa including the anchoring fibrils in a labelling pattern similar to that of the monoclonal antibody (LH7.2) to collagen VII. All the autoantibodies binding to the hemidesmosome or lamina lucida recognized a protein in epidermal extracts of molecular weight 180 kDa or its breakdown product of 97 kDa, 200 kDa or 230 kDa. The antibodies binding to the lamina densa recognized proteins of 180 and 285 kDa. The antibodies that bound to the lamina densa and anchoring fibrils recognized collagen VII. In this immunogold EM study we have shown four patterns of IgA labelling in six patients with LAD, associated with five different antigens as recognized by immunoblotting. These results, together with our previous immunofluorescence and immunoblotting findings add support to the contention that LAD is a heterogeneous disease as regards both the target antigens and epitopes.

There was variation in the autoantibody response within the disease and the patient, with regard to target molecules and autoantibody class. The finding that IgG as well as IgA autoantibodies predominantly target BP180 supports a pivotal role for collagen XVII in adult and childhood LAD. The IgG response was very restricted compared with IgA autoantibodies (P < 0.01). Autoantibodies from children had a more restricted antigen repertoire than from adults (P < 0.05). Epitope spreading is common in LAD and is affected by the class of autoantibody and age of the patient.

This study examines in detail the HLA associations of 74 patients (40 women and 34 men) with bullous pemphigoid (BP) and compares their immunogenetic profile with that of 604 unrelated control subjects (238 women and 366 men). Correlations were sought between HLA antigens and the various BP disease parameters investigated. The presence of milia was the only clinical or laboratory finding which was linked with a specific HLA antigen, HLA-DQ6, in both men and women with BP (P < 0.01). BP has previously been linked with the HLA-DQ7 antigen and this association was confirmed in 39 of our patients (14 women and 25 men). Twelve of these patients (four women and eight men) were homozygous for HLA-DQ7. The association of HLA-DQ7 with BP was gender-restricted and only significant for men (P < 0.01). No equivalent HLA disease susceptibility risk factor could be identified for our female BP patients. This difference in HLA association between men and women with BP has not been reported previously, and its significance for disease pathogenesis is not known. No specific link could be found between HLA-DQ7 and BP for any of the clinical, immunofluorescence, western blotting, treatment or prognostic disease factors studied.