Ans: A (Pemphigus vulgaris) Ref: Vesiculobullous Disorders. In: Thappa DM, editor. Essentials in Dermatology, 2nd ed., Jaypee 2009; 114-26).Explanation:Pemphigus is an autoimmune blistering disorder characterized by autoantibody formation against the intercellular cementing substance called desmogleins.The mechanism of cell separation is called acantholysis- loss of intercellular substance causing separation of the epidermal keratinocytes which become rounded-result in intraepidermal blister.These large rounded keratinocytes with large nucleus, perinuclear halo and peripheral condensation of cytoplasm are called the acantholytic ceils - seen in Tzanck smear.Types of pemphigus:Pemphigus vulgaris (variant-pemphigus vegetans)- most common typePemphigus foiiaceus (variant-pemphigus erythematosus; endemic pemphigus or fogoselvagem)Paraneoplastic pemphigusDrug induced pemphigusIgA pemphigusNeonatal pemphigusClinical features:Fluid filled bullae - rupture - painful erosions with no tendency to spontaneous healing.Painful mucosal erosions- oral (most common: almost in all cases in pemphigus vulgaris); genital mucosa, pharynx, larynx,conjunctiva, urethraBulla spread sign/ Asboe Hansen sign- positive.Nikosky sign- peeling of skin leaving behind erosions when tangential pressure applied over areas of normal looking skin or over bony prominences (other conditions- staphylococcal scalded skin syndrome, toxic epidermal necrolysis).Diagnosis:Tzanck smear- acantholytic cells; histopathology; direct and indirect immunofloresence.Treatment:Systemic steroids are mainstay of treatment.Adjuvants- cyclophosphamide, azathioprine, methotrexate, mycophenolate mofetil, dapsone. plasmapheresis, iv immunoglobulins; biological agent- Rituximab (anti CD20). (See Table 19)