Pemphigus vulgaris is best described as which type of hypersensitivity?

• A. Pemphigus vulgaris
• B. Serum sickness
• C. Hashimoto's thyroiditis
• D. Guillain-Barre syndrome

Answer: (A)

Type II hypersensitivity is antibody-mediated against cell-surface or extracellular matrix antigens. In pemphigus vulgaris, autoantibodies of the IgG class target desmoglein proteins in desmosomes that hold keratinocytes together. This binding disrupts keratinocyte adhesion (acantholysis), causing intraepidermal blisters. The pathology shows suprabasal splits with a “row of tombstone” basal cells, and direct immunofluorescence reveals a characteristic intercellular (fishnet) pattern of IgG and C3 in the epidermis. Clinically, mucosal involvement and a positive Nikolsky sign reflect this loss of cell–cell adhesion. This mechanism is distinct from serum sickness, which is immune complex–mediated (type III), and from Hashimoto’s thyroiditis (primarily T-cell–mediated, type IV) or Guillain-Barré syndrome (autoimmune demyelination).