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.