Spontaneous autoimmune subepidermal blistering diseases in animals: a comprehensive review

Autoimmune subepidermal blistering diseases (AISBDs) are rare skin disorders of animals that were first identified in dogs but several AISBDs are now recognised in other companion animal species. Most AISBDs in animals are homologues of the human diseases and are thought to share similar pathomechanisms of epidermal and/or mucosal blister formation caused by autoantibodies targeting structural proteins of the basement membrane zone (BMZ). Disruption of their structural function by the autoantibodies and/or recruited inflammation leads to BMZ fragility, which presents clinically as vesicles, bullae and, later, deep erosions and ulcers. Canine AISBDs are the best characterised, particularly the more common variants such as mucous membrane pemphigoid (48%), epidermolysis bullosa acquisita (EBA) (26%), and bullous pemphigoid (10%). Exceedingly rare AISBDs in the dog are junctional EBA, mixed AISBD, type-1 bullous systemic lupus erythematosus, linear IgA dermatosis, and pemphigus gestationis. The diagnosis of a specific AISBD is made by combining the clinical features (breed, age, lesion distribution) with histological evidence of subepithelial clefting, but not all AISBDs can be differentiated in this manner and specialised immunological testing is required. This latter, unfortunately, is not readily available and, therefore, the specific AISBD diagnosis often remains unconfirmed. While this limits further understanding of these diseases, it does not prevent clinicians from treating their patients, as the treatment approaches are similar for the different AISBDs in dogs. This review primarily focuses on canine AISBDs, the species for which these diseases have been best characterised, and shorter descriptions of variants in other species are also provided.

Epidermolysis bullosa acquisita in a great Dane

Autoimmune subepidermal blistering diseases in dogs were all classified as bullous pemphigoid until 1998. Since then, refinements in reagents and immunological techniques have allowed diseases which are histologically similar but which have a different molecular pathogenesis to be described. This report describes the first case of one such disease, epidermolysis bullosa acquisita, to be documented in the UK. The dog presented with a severe blistering and ulcerative disease affecting the oral cavity, pinnae and distal limbs. The diagnosis was confirmed by histopathology and direct and indirect immunofluorescent demonstration of immunoglobulin G reactivity to basement membrane antigens. Treatment with glucocorticoids, azathioprine, colchicine and an intravenous infusion of immunoglobulins resulted in complete resolution. The drugs were discontinued 12 months after the start of treatment and the dog remained in remission.

Development of an owner-assessed scale to measure the severity of pruritus in dogs

Assessment of pruritus is critical in dermatological history taking, both for initial diagnosis and for monitoring treatment. Various methods of assessing pruritus in the dog have been described but none have been validated. In this study, four different pruritus scales were initially assessed: a 0-5 numerical scale; a scale containing six categories of pruritic behaviours; a scale with six basic descriptors of severity; and a visual analogue scale with severity descriptions at either end. One hundred and sixteen owners were asked to grade their dog's pruritus with each of the four scales given to them in a randomized order, and asked which they thought was easiest to use, which was most accurate in assessing their dog's pruritus level, and which two scales they would combine to make a superior scale. Pruritus scores from different scales were highly correlated with each other, but scores were significantly higher with the severity and numerical scales compared to the behaviour scale. Based on the clients' responses, a new scale was developed that combined features of the behaviour and severity-based scales with the visual analogue scale. When tested on 166 different owners, 98% thought it was easy to use and accurate in assessing their dog's pruritus level. In 44 dogs, independent scores obtained by two owners were highly correlated (R = 0.8; P < 0.0001), confirming the scale's repeatability. The new scale proved to be an easy and repeatable method for owners to determine the severity of pruritus in their dog.