Basic and Clinical Sciences (BCSE) Practice Exam

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How do pemphigoid and pemphigus differ in pathology?

  1. Pemphigoid involves debris on mucosal surfaces

  2. Pemphigus affects the basement membrane with linear IgG bands

  3. Pemphigus shows erosions and bullae, while pemphigoid demonstrates IgG on the epidermis

  4. Pemphigoid is a type IV reaction while pemphigus is Type I

The correct answer is: Pemphigus affects the basement membrane with linear IgG bands

Pemphigus and pemphigoid are both autoimmune blistering diseases but differ significantly in their underlying pathology. Pemphigus primarily affects the connections between skin cells, specifically the desmosomes, leading to intraepithelial blistering. In this condition, antibodies are formed against desmosomal proteins, resulting in loss of cohesion between keratinocytes. This causes fragile blisters that can rupture easily, leading to painful erosions on the skin and mucosal surfaces. The correct response highlights a key feature of pemphigus, which includes the presence of linear IgG deposits at the cell surface junctions, indicative of the autoimmune response directly affecting the epidermal layer, and the resultant acantholysis (separation of skin cells). In contrast, pemphigoid involves antibodies directed against proteins in the basement membrane zone, leading to subepithelial blistering, where blister formation occurs below the epidermis. Recognizing these key differences is essential for understanding the clinical presentations, histopathological findings, and treatment strategies for each condition. The other choices presented relate to various features of pemphigus and pemphigoid but fail to capture the primary distinction regarding the site of antibody action (epidermis versus basement membrane), which