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Vesiculobullous Skin Diseases

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Vesiculobullous Skin Diseases

Dr. Sami Fatehi

MD, MSc, PhD

Vesiculobullous Skin Diseases

  • Bullous diseases are skin conditions characterized by blister formation.
    • Bullae (blisters) are an accumulation between the epidermis or upper dermis.

Causes of Blisters

  1. Genetic since birth or in early life
  2. Physical (heat or friction)
  3. Inflammatory (eczema)
  4. Immunologic (autoimmune reaction)
  5. Non-immunologic (drug reaction)

How Are Keratinocytes Held Together?

  • There are two levels holding:
    1. Between keratinocytes: ⇒ desmosomes
    2. Between basal keratinocytes and basement (dermis): ⇒ hemidesmosomes

Structure of the Epidermis and Sites of Target Antigens/Cleavage in Bullous Diseases

Keratinocytes and Desmosomes

  • Keratinocytes in the epidermis are tightly bound together by desmosomes and intercellular substance for a barrier with high tensile strength and stability.
  • Basal keratinocytes bind to hemidesmosomes.

Basement Membrane Zone (BMZ)

  • BMZ lies beneath the epidermis as specialized area of cell- extracellular matrix adhesion.

  • Collagens & laminins traversing the zone forming hemidesmosomes and anchor the epidermis to the dermis

BMZ Structure

  • BMZ is divided into:
    1. Lamina lucida
    2. Lamina densa
    3. Sub lamina densa
  • The BMZ is vulnerable to damage or malformation and is a common site of blister formation, particularly the lamina lucida.

Classification and Pathophysiology of Bullous Diseases

  1. Intra-epidermal bulla → the base and the roof of the bulla are epidermal cells → bulla is flaccid and easy to be ruptured
  2. Sub-epidermal bulla → the base is the dermis and the roof is the epidermis → bulla is tense and stable

Detailed Classification and Pathophysiology of Bullous Diseases

  1. Intraepidermal bullae:

    • A. Acantholytic bullae: This is due to the breakdown of desmosomes
    • B. Nonacantholytic bullae: It is due to the death of the cells or physical destruction

  2. Subepidermal bullae: Lesions formed between the epidermis and the lamina propria of the dermoepidermal junction like:

    1. Bullous Pemphigoid
    2. Epidermolysis Bullosa

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