**Question:** A 60 year's old male patient presented with blisters over trunk and thighs for 2 weeks. Lesions are mildly itchy. On examination blisters were tense with erythematous base. Nikolsky's sign is negative. There was no mucosal involvement.

**Core Concept:**
The question presents a case of a patient presenting with vesicular skin lesions consistent with bullous disorders. Nikolsky's sign is negative, indicating that the blisters are not due to bullous pemphigoid, a common autoimmune bullous disorder where the blisters are fragile and bleed on mild pressure.

**Why the Correct Answer is Right:**
The correct answer, **A** (Erythema Multiforme), is chosen due to the patient's age, presentation, and the absence of mucosal involvement. Erythema multiforme is a group of skin disorders characterized by symmetric, targetoid, erythematous macules and bullae, with mucosal involvement typically seen in its severe form. In this case, the patient does not have mucosal involvement, indicating that the correct answer is not **B** (Herpes Simplex, **C** (Contact Dermatitis), or **D** (Sweet Syndrome)).

**Why Each Wrong Option is Incorrect:**

**B.** Herpes Simplex: Herpes simplex is a viral infection caused by herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2). The case described does not show mucosal involvement, which is a characteristic feature of herpes simplex infection.

**C.** Contact Dermatitis: Contact dermatitis is an allergic reaction due to an allergic contact with a specific substance. The patient's age, lack of mucosal involvement, and mild itching are inconsistent with contact dermatitis.

**D.** Sweet Syndrome: Sweet syndrome is a rare, acute, neutrophilic dermatosis characterized by painful, erythematous, tender plaques or nodules, and painful, erythematous, and indurated plaques. The case described does not show mucosal involvement, which is a characteristic feature of Sweet syndrome.

**Clinical Pearl:**
Erythema multiforme is a group of skin disorders characterized by symmetric, targetoid, erythematous macules and bullae, with mucosal involvement typically seen in its severe form. In this case, the patient does not have mucosal involvement, making the correct answer (A) the appropriate choice. Erythema multiforme can be triggered by infections (e.g., herpes simplex, varicella zoster virus, and Mycoplasma pneumoniae) or drugs (e.g., sulfa drugs, penicillin, and antimalarial drugs).

**Why Each Wrong Option is Incorrect:**

**B.** Herpes Simplex: Herpes simplex is a viral infection caused by HSV-1 or HSV-2. The patient's age and lack of mucosal involvement make this option unlikely.

**C.** Contact Dermatitis: Contact dermatitis is an allergic reaction