Pemphigus Vulgaris

Pemphigus vulgaris is an autoimmune blistering disorder in which IgG4 autoantibodies target desmoglein-1 and/or desmoglein-3. These proteins act like the fasteners holding neighbouring keratinocytes together. When the fasteners are disrupted, the cells separate through acantholysis, creating a split within the epidermis. Because the split is relatively superficial, the blisters are flaccid rather than tense. They rupture with minor contact and leave painful, moist erosions. Oral lesions are common and may appear before the skin findings; pharyngeal, esophageal, or genital involvement can make swallowing, eating, and hydration difficult. Antibody involvement of desmoglein-3 tends to produce mucosal disease, while involvement of both desmoglein-3 and desmoglein-1 produces mucocutaneous disease. A positive Nikolsky sign—epidermal separation with lateral pressure—can support the clinical impression, but deliberately rubbing fragile skin can enlarge the wound. Assess gently rather than provoking new denudation. The high-yield visual distinction is between pemphigus vulgaris and bullous pemphigoid: pemphigus produces fragile, flaccid bullae and erosions, whereas bullous pemphigoid typically produces tense, deeper blisters. The appearance suggests the diagnosis; tissue testing confirms it.