**Question:** A 6-month-old infant presented with multiple papules & exudative lesions on the face, scalp, trunk and few vesicles on palms and soles for 2 weeks. His mother has h/0 itchy lesions. The most likely diagnosis is –

A. Discoid lupus erythematosus
B. Pemphigus vulgaris
C. Urticaria
D. Eczema

**Correct Answer:** B. Pemphigus vulgaris

**Core Concept:**
Pemphigus is a group of autoimmune diseases characterized by blistering of the skin and/or mucous membranes. It is caused by the production of autoantibodies that target and damage desmoglein proteins, which are essential for maintaining epidermal adhesion. The two main types of pemphigus are pemphigus vulgaris and pemphigus foliaceus. Pemphigus vulgaris is characterized by the presence of vesicles and bullae on both skin and mucous membranes, while pemphigus foliaceus affects the skin only.

**Why the Correct Answer is Right:**
Pemphigus vulgaris is the right answer because the patient presents with multiple papules and exudative lesions on the face, scalp, trunk, and few vesicles on palms and soles, which is consistent with the clinical picture of pemphigus vulgaris. The presence of exudative lesions and bullae is indicative of an autoimmune disease affecting the skin and mucous membranes.

**Why Each Wrong Option is Incorrect:**

A. Discoid lupus erythematosus: This is a distinct entity, characterized by discoidal plaques and is less common in pediatric age groups. It is also less likely to present with vesicles and bullae.

C. Urticaria: Urticaria is characterized by raised, red, and itchy lesions that are commonly triggered by allergens, stress, or infections. It does not involve bullae formation.

D. Eczema: Eczema is a group of conditions characterized by dry, red, and itchy skin lesions. It is not associated with bullae formation.

**Clinical Pearl:**
In cases of suspected pemphigus vulgaris, a thorough family history should be taken, with a focus on pemphigus vulgaris in first-degree relatives. A positive family history is strongly suggestive of the diagnosis and can help guide further management strategies.

For example, if the mother or sibling has pemphigus vulgaris, the diagnosis is much more likely, and the treatment approach may differ from that for sporadic cases.