Epidermolysis Bullosa Acquisita
This is a mechanobullous subepidermal autoimmune blistering disorder that usually begins in adulthood. Patients with epidermolysis bullosa acquisita (EBA) should have a negative family and personal history of blistering disorders in order to make the diagnosis.
The classic presentation consists of skin fragility, noninflammatory bullae, and erosions in an acral distribution that heal with scarring and milia formation. Nail dystrophy and scarring alopecia may also be present. About one quarter of EBA patients will have a more inflammatory presentation similar to bullous pemphigoid patients with widespread, tense bulllae on inflamed or urticarial skin of the trunk and extremites. Rarely, these patients will present with only urticarial plaques. Pruritus is a prominent feature. About 10% of patients will present with mostly mucosal involvement similar to that seen in patients with cicatricial pemphigoid. Finally, a small number of patients will have a clinical presentation reminiscent of Brunsting-Perry cicatricial/bullous pemphigoid with vesiculobullous lesions localized to the head and neck that heal with residual scars.
Histopathologic exam reveals a subepidermal blister. Patients with the more classic presentation demonstrate a sparse inflammatory infiltrate while lesions reminiscent of bullous pemphigoid have a more significant inflammatory infiltrate with eosinophils. On electron microscopic exam, immune deposits are found within the lower lamina densa or sublamina densa. Direct and indirect immunofluorescence studies demonstrate linear IgG at the dermoepidermal junction similar to that found in bullous pemphigoid. To distinguish these two disorders, salt-split skin studies must be performed. In EBA lesions, IgG binds to the base of the blister reflecting IgG antibody binding to type VII collagen (the protein component of anchoring fibrils). In contrast, in salt-split skin analysis from BP patients, the BP antigens (BPAG1 and BPAG 2) bind the epidermal side of the split and so in this disorder, IgG binds to the roof of the blister.
EBA may be associated with other autoimmune diseases, most frequently inflammatory bowel disease. It is often difficult to treat and patients tend to have a chronic course.