Rare variants of pemphigoid diseases

Pemphigoid diseases comprise a heterogeneous group of subepidermal autoimmune blistering dermatoses characterized by autoantibodies against structural proteins of the dermal-epidermal junction. Recent decades have witnessed a significant surge in the incidence of these diseases, which, in addition to general aging of the population, can be attributed to the availability of precise diagnostic methods and improved knowledge of the clinical and immunopathological spectrum. While bullous pemphigoid, mucous membrane pemphigoid, and linear IgA disease account for most pemphigoid disorders, less frequent, presumably underdiagnosed variants are increasingly becoming relevant for clinicians. These include epidermolysis bullosa acquisita, anti-p200 pemphigoid, pemphigoid gestationis, lichen planus pemphigoides, and recently defined entities such as IgM pemphigoid and Orf-induced pemphigoid. Accurate characterization and differentiation of these subtypes are not only of diagnostic relevance but may also be associated with therapeutic and prognostic implications for affected individuals. Due to the rarity of these diseases, no controlled prospective clinical trials currently exist, making their diagnosis and therapy challenging.