B. Bhogal

Chronic bullous disease of childhood, childhood cicatricial pemphigoid, and linear IgA disease of adults: A comparative study demonstrating clinical and immunopathologic overlap

Linear IgA disease of adults, chronic bullous disease of childhood, and the rare childhood cicatricial pemphigoid currently are regarded as separate clinical entities despite their many shared features. All are sulfone-responsive subepidermal bullous diseases associated with linear IgA deposition at the basement membrane zone. In this paper we present a long-term study of 25 cases of adult linear IgA disease, 25 cases of chronic bullous disease of childhood, and four cases of childhood cicatricial pemphigoid, which has revealed further similarities among all three groups. The morphology and distribution of the cutaneous and mucosal lesions were similar; mucosal involvement was present in 80% of patients with adult linear IgA disease, 64% of those with chronic bullous disease of childhood, and 100% of those with childhood cicatricial pemphigoid, and ocular scarring affected patients in all groups. Remission occurred in 64% of those with chronic bullous disease of childhood (the disease was active in 12% after puberty), 48% of those with adult linear IgA disease, and in no cases of childhood cicatricial pemphigoid. HLA B8 and circulating IgA anti-basement membrane zone antibody were more common in chronic bullous disease of childhood than adult linear IgA disease. There were no absolute differences among the three groups, and we suggest that adult linear IgA disease, chronic bullous disease of childhood, and childhood cicatricial pemphigoid are the same disease, with childhood cicatricial pemphigoid being a more severe form of chronic bullous disease of childhood.

The severity of cutaneous and oral pemphigus is related to desmoglein 1 and 3 antibody levels.

Background Pemphigus vulgaris (PV) and foliaceus (PF) are characterized by antibodies to the desmosomal proteins desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1), respectively. Past studies using indirect immunofluorescence (IIF) as a measure of pemphigus antibody levels have failed to demonstrate consistently a relationship between disease severity and IIF titres. However, IIF is not able to measure separately Dsg1 and 3 antibodies, unlike enzyme‐linked immunosorbent assays (ELISA), which utilize recombinant proteins.

Identification of the target antigen in chronic bullous disease of childhood and linear IgA disease of adults.

Disease‐associated autoantibodies to basement membrane proteins have been used to characterize structural components of the epidermal basement membrane such as bullous pemphigoid (BP) antigen and epidermolysis bullosa acquisita (EBA) antigen (type VII collagen). The autoimmune bullous diseases characterized by IgA autoantibodies to the basement membrane zone (BMZ). i. e. linear IgA disease of adults (LAD) and chronic bullous disease of childhood (CBDC) may have circulating antibodies. Previous studies of tissue distribution and ultrastructural binding have suggested that the LAD and CBDC antigens are similar, if not identical, and differ from the target antigens of the other bullous diseases. We present the molecular characterization of the LAD/CBDC antigens by Western blotting of a large series of antisera. Seven of 33 sera (21%) were positive on immunoblotting and bound to the same antigen which has a molecular weight (MW) of 285 kDa. Using both defined polyclonal antisera to BP and LH 7.2 monoclonal antibody to type VII collagen (carboxy terminal) we have shown that the LAD and CBDC antisera both bind to an identical molecular weight protein which clearly differs from both the BP and EBA (type VII collagen) antigens. Although detectable in dermal tissue extracts like EBA, the MW of 285 kDa is heavier than type VII collagen (250 kDa, in our system, using non‐collagenous standards). This study confirms the identity of LAD and CBDC antigens to be the same and to differ from previously described basement membrane proteins.

A study of benign chronic bullous dermatosis of childhood and comparison with dermatitis herpetiformis and bullous pemphigoid occurring in childhood

Eighteen patients with benign chronic bullous dermatosis of childhood were studied and the findings compared with those of dermatitis herpetiformis (twenty‐two cases) and bullous pemphigoid (five cases) beginning in childhood.

A comparative study of toxic erythema of pregnancy and herpes gestationis.

We compared the clinical features, histopathology, immunopathology and immunogenetics of 30 patients with toxic erythema of pregnancy and 24 patients with herpes gestationis. Although we found some clinical and histopathological overlap we highlighted several important differences. In toxic erythema of pregnancy prominent striae were frequently present. Herpes gestationis was suggested by the occurrence of periumbilical lesions, acute exacerbations immediately after delivery, and persistence of the eruption for more than 3 weeks post‐partum. In herpes gestationis, immunofluorescence studies were consistently positive, there was a high frequency of HLA‐B8 and an association with autoimmune thyrotoxicosis. Toxic erythema of pregnancy did not share these immunological features. Therefore we feel that toxic erythema of pregnancy and herpes gestationis should continue to be classified as separate disorders.

Immunoblotting studies of linear IgA disease

Patients with linear IgA deposits at the basement membrane zone (BMZ) detected by direct immunofluorescence (IF) may show diverse clinical and laboratory findings. The aim of this study was to investigate the issue of target antigens for linear IgA disease (LAD) antibodies. We examined sera from 46 adults and children with exclusive IgA deposits at the BMZ, by both indirect IF on 1 M NaCl split human skin and immunoblotting. IgA anti-BMZ antibodies binding to the epidermal side of the split were found in 31 LAD sera. IgA anti-BMZ antibodies binding to the dermal side of the split were detected only in 4 LAD sera. No sera contained IgA anti-BMZ antibodies binding to both sides of the split. Immunoblotting revealed that 12 epidermal side-positive LAD sera reacted with the 97 kDa protein in the human epidermal extracts. Moreover, we found that 2 dermal side-positive LAD sera reacted with a protein of approximately 255 kDa on immunoblotting of the dermal extract. We conclude that there are at least two types of LAD. However, the nature of target antigens for LAD antibodies remains to be determined.

Analysis of antigens targeted by circulating IgG and IgA autoantibodies in 50 patients with cicatricial pemphigoid.

In this study we investigated sera from 50 typical cicatricial pemphigoid (CP) patients. By indirect immunofluorescence on 1 M NaCl-split human skin sections, IgG of 17 sera and IgA of 22 sera reacted with the epidermal side of the split, while IgG of two sera reacted with the dermal side. These latter two sera were later confirmed to be anti-epiligrin CP. By immunoblotting of epidermal extracts, IgG of 14 sera reacted with the 230 kD bullous pemphigoid (BP) antigen (BP230). IgG of 15 sera and IgA of 11 sera reacted with the 180 kD BP antigen (BP180). Interestingly, a bacterial fusion protein containing the BP180 NC16a domain was recognized by IgG of 18 sera but not by IgA of any sera. Fusion proteins containing the C-terminal region of BP180 were recognized by IgG of 20 sera, but it was detected by IgA of only two sera. Our results suggest that, although CP sera show very low titers of autoantibodies, a considerable number of sera contain IgG antibodies to BP180 (either NC16a or C-terminal domain), confirming previous studies. In addition, we showed that greater numbers of IgA antibodies react with BP180, seemingly with different types of epitopes from those for IgG antibodies. Because the specificity of IgG antibodies is not very different from those in BP, IgA antibodies may play a specific role for the development of characteristic clinical features in CP. Future studies should elucidate the pathogenic role of the IgA antibodies in CP.

A case of linear IgA bullous dermatosis with IgA anti-type VII collagen autoantibodies

Summary In this study we present a patient with the sublamina densa type of linear IgA bullous dermatosis (LABD). with IgA autoantibodies reactive with the 290‐kDa type VII collagen (the epidermolysis bullosa acquisita (EBA) antigen) and with immunoblotting of normal human dermal extracts. The clinical and histological features of the present case were compatible with those of LABI) but quite different from those of RBA. Although EBA sera reacted with the bacterial fusion protein of the N‐terminal globular (NC1) domain of type VII collagen, this patients serum did not show reactivity. Furthermore, ultrastructural localization of target epitopes on the anchoring fibrils in this patient was considerably different from EBA. These results indicate that, whereas EBA antibodies react with the NC1 domain of type VII collagen, the epitope in this case is different from that of EBA (and is most likely on the central triple helical domain). This difference may be responsible for the clinical presentation in this patient being distinct from that of EBA.

Diagnosis of pemphigus by ELISA: a critical evaluation of two ELISAs for the detection of antibodies to the major pemphigus antigens, desmoglein 1 and 3

Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are characterized by autoantibodies to the desmosomal glycoproteins desmoglein 3 (Dsg 3) and Dsg 1 (Dsg 1), respectively. In this study, two enzyme‐linked immunosorbent assays (ELISA) which detect IgG autoantibodies to Dsg 1 and Dsg 3 have been evaluated. A total of 317 normal and disease controls, 82 patients with PV and 25 with PF were studied. The Dsg 3 ELISA was positive in all 34 patients with untreated PV and the Dsg 1 ELISA was positive in all 10 with untreated PF. When patients undergoing treatment were included, the sensitivities fell to 95% and 92%, respectively, but still compared favourably to the sensitivity of indirect immunofluorescence which was 79% in PV and 84% in PF. All PF sera were negative in the Dsg 3 ELISA and the specificity of both assays was 98% or greater. Large numbers of samples could be analysed simultaneously over a relatively short time period. The Dsg 1 and Dsg 3 ELISAs also provided objective, quantitative, reproducible data which allowed differentiation of PV from PF and in view of these advantages, they are likely to become a routine technique in diagnostic laboratories.

The distribution of IgG subclasses in pemphigoid gestationis: PG factor is an IgG1 autoantibody

Using monoclonal antibodies in immunofluorescence techniques, the subclass distribution of anti-basement membrane zone IgG antibodies was studied in the skin, placenta, and serum of patients with pemphigoid (herpes) gestationis. IgG1 was found to be the major IgG subclass in both serum and tissue, being detected in the sera of all pemphigoid gestationis patients studied. In pemphigoid and pemphigus, however, the distribution of IgG subclasses was heterogeneous, with IgG4 being the dominant autoantibody. Pemphigoid (herpes) gestationis factor, the circulating anti-basement membrane zone autoantibody thought to be pathogenic in pemphigoid gestationis, is therefore, an IgG1 antibody, with inferred complement binding capacity. Tissue damage in pemphigoid gestationis is apparently mediated by complement fixation which is detected via the classical complement cascade.