Characterizing Distinct Subtypes of Autoimmune Blistering Skin Diseases

The laboratory and clinical characteristics of immunoglobulin A (IgA)-mediated epidermolysis bullosa acquisita (EBA) compared with linear IgA bullous dermatosis (LABD) was described in study data published in JAMA Dermatology. Given its clinical profile and the intensive treatment required, investigators suggested that EBA be considered a separate disease entity from LABD.

IgA-mediated EBA is an autoimmune blistering skin condition currently considered to be part of the LABD disease spectrum. The clinical features of IgA EBA are poorly characterized due to the small number of reported cases. To inform this gap, investigators extracted data from an autoimmune disease diagnostic laboratory in Germany. Patients diagnosed with LABD, IgA EBA, and IgG EBA from October 2010 to July 2019 were included in the study. IgG-mediated EBA, a more common condition than IgA-mediated EBA, comprises its own distinct disease category. Investigators conducted a retrospective analysis of the clinical features and laboratory figures of each diagnostic category.

The retrospective review yielded 300 total cases: 21 with IgA EBA (57% women); 222 with LABD (51% women); and 57 with IgG EBA (51% women). Age of onset varied significantly between groups: median (range) age at diagnosis was 64 (4-81) years for IgA EBA, 56 (3-92) years for IgG EBA, and 70 (1-94) years for LABD. Age of onset did not appear to vary by sex. The clinical presentation of IgA EBA was heterogenous and differed significantly from LABD. There were 4 patients with IgA EBA who were described in depth: 2 presented with “blistering…wheals resembling bullous pemphigoid,” and the remaining 2 had excoriated papules. In all cases, skin lesions involved the upper and lower extremities. Lesions were present in the trunk in 1 case, the oral mucosa in 2 cases, and the nasal mucosa in 1 case. All patients received treatment with dapsone, the primary treatment option for LABD. Only 1 case achieved remission with dapsone; another case required concomitant treatment with intravenous dexamethasone, topical corticosteroids, and mycophenolate mofetil. The remaining 2 patients achieved only partial remission despite combination treatment with dapsone and various other biologic and/or steroid agents.

Based on the distinct clinical features and poor overall response to primary LABD treatment, investigators recommended that IgA EBA be considered its own disease. However, given the small number of studied cases, further study is necessary to better profile IgA EBA.

“Results of this study support that…IgA-mediated cases of [pemphigoid diseases] are not part of the spectrum of LABD but instead constitute a separate disease phenotypically closer to EBA, and may be more common than previously thought,” investigators wrote.

Reference

Becker M, Schumacher N, Schmidt E, Zillikens D, Sadik CD. Evaluation and comparison of clinical and laboratory characteristics of patients with IgA epidermolysis bullosa acquisita, linear IgA bullous dermatosis, and IgG epidermolysis bullosa acquisita. JAMA Dermatol. Published online June 23, 2021. doi: 10.1001/jamadermatol.2021.0762