Vitiligo Vulgaris

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Vitiligo Vulgaris

• By Drew Compton

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Overview

• Vitiligo affects approximately 1 of the
  worldwide population.
• Depigmented patches on the hands, neck,
  genitalia, limbs, and face.

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Subtypes of Vitiligo

• Differ by anatomical location, and size of
  lesions
• Focal - a few isolated lesions
• Segmental unilateral distribution
• Acrofacial fingers and around mouth
• Universal almost total depigmentation
• Generalized most common, symmetrical
  distribution, form that will be discussed

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Psychological Aspects

• Can cause severe psychological and social damage
• Can result in discrimination especially in 3rd
  world countries.
• Can be confused with Leprosy

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Cytology

• Normal skin is pigmented with melanin that is
  produced by melanocytes
• Detection by Masson Silver Stain
• Therefore white spots are due to melanocyte death

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Hypothesized Causes

• Neural Neuron terminates on melanocyte and
  causes neurotransmitter toxicity
• Autocytotoxic Defective enzyme in Hydrogen
  Peroxide breakdown. H2O2 disrupts melanin
  production pathway
• Autoimmune Patients own immune system attacks
  and destroys the melanocytes

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Support for Autoimmune Theory

• Presence of Vitiligo increases the chances of
  developing other autoimmune diseases
• Examples Hashimotos Thyroiditis, Pernicious
  Anemia, Insulin-dependant Diabetes, Systemic
  Lupus Erythemetosus.

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Autoimmunity

• Patients immune system attacks healthy tissues
  within the body
• It has been shown that both Cell-mediated and
  Humoral immunity are active in Vitiligo
• The two types work cooperatively to produce
  melanocyte destruction

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Humoral Immunity

• B cell mediated production and excretion of
  proteins called antibodies to fight
  extra-cellular pathogens (example - bacteria)
• Antibodies bind to the target and initiate a
  complex immune reaction that culminates in target
  cell destruction
• Humoral immunity was proven to be active in
  Vitiligo by the discovery of Melanocyte reactive
  auto-antibodies (IgG-anti-MC)

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Immunoglobulin Structure
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ELISA
Optical Density of patients serum was
significantly different from controls
Melanocyte
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Cell-Mediated Immunity

• T cells recognize and destroy abnormal cells
• Most effective against intra-cellular pathogens
  (example - viruses)
• A correlation has been made between T cell
  concentration and melanocyte death
• This shows that cell-mediated immunity is active
  in Vitiligo.

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How was this discovered?

• Different cell types were identified by staining
  for specific cell surface proteins
• This showed that the highest concentration of T
  cells was within .6 mm of the lesional border
• This shows that T cell concentration is
  significantly correlated with melanocyte death
  suggesting that T cells are the true melanocyte
  killers

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Proposed Cooperativity

• The current theory for vitiligo pathogenesis is
  that humoral immunity promotes cell-mediated
  destruction of melanocytes
• Anti-melanocyte antibodies induce macrophages to
  produce cytokines that attract T cells.
• T cells then infiltrate and kill the melanocytes

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Cytokines

• Cytokines are small signaling molecules important
  in cell to cell communication
• These cytokines increase the amount of
  intercellular adhesion molecules (ICAMS) on blood
  vessel walls
• ICAMS allow lymphocytes, in this case T cells, to
  escape the vasculature

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Extravasation
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Melanocyte Killers

• These cytokine activated T cells escape the
  vasculature and infiltrate the skin
• They then move toward the source of the
  cytokines, which in Vitiligo, is the dermis
• This puts the T cells and melanocytes in close
  proximity and facilitates lethal cell-cell
  interactions

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Recap of Autoimmune Theory

• Autoimmunity - B cells produce Anti-melanocyte
  antibodies that attach to the surface of a
  melanocyte and induce local macrophages to
  produce cytokines
• These cytokines attract T cells into the area,
  and it is believed that these cells mediate
  destruction of the melanocytes.

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Dont Forget These are People