Learning Objective

Describe the clinical features, pathogenesis, and major subtypes of eczema, and differentiate between acute and chronic eczematous reactions.

Eczema refers to a group of inflammatory skin diseases characterized by pruritus, erythema, and epidermal spongiosis (intercellular edema of the epidermis).

Acute Eczema

• Presents with vesicular, erythematous, and pruritic lesions.
• Prominent spongiosis on microscopy.

Chronic Eczema

• Results from repetitive scratching.
• Characterized by:
  • Lichenification (thickened skin)
  • Dry, hyperkeratotic plaques

Major Subtypes of Eczema

Atopic Dermatitis

• Often inherited.
• Associated with filaggrin (FLG) gene mutations, causing:
  • Defective epidermal barrier
  • Increased susceptibility to irritants and allergens
• Common in children; associated with asthma and allergic rhinitis.

Contact Dermatitis

Two forms:

1. Allergic Contact Dermatitis
   1. Type IV hypersensitivity
   2. Examples: poison ivy, nickel in jewelry
2. Photocontact Dermatitis
   1. Triggered when a chemical on the skin reacts with sunlight
   2. Example: photosensitivity from tetracycline