Skin Diseases Affecting Multiple Layers

• Psoriasis Vulgaris
  • Very common, often familial disease. The lesion consists of a dense scale overlying a dense, thickened plaque
  • Demonstrates histologic epidermal proliferation (acanthosis) and highly characteristic parakeratosis.
  • One of the causes may be a T-cell defect

  

  • Histology
    • Elongated dermal papillae.
    • Lots of proliferation in the stratum malphigii resulting in a thicker stratum malphigi and stratum corneum (acanthosis forming a plaque)
    • The stratum corneum is immature, and shows a marked parakeratosis forming a scale (hyperkeratosis with retention of nuclei or keratinocytes).
    • Cells travel thru the epidermis (from the stratum basale to the stratum corneum) much faster (in 8 days as opposed to near 30 days, normally).
    • Neutrophilic abscesses may be present in either the stratum corneum or stratum malphigii.
      • If neutrophil infiltration is prominent, we see Pustular Psoriasis
        • Pustules form usually on the palms and soles, though there is no bacterial infection. Thus, treatment with antibiotics is worthless and will only disrupt normal flora.

         

• Lichen Planus
  • Has an obscure etiology
  • Grossly
    • Characterized by well demarcated, purplish, flat-topped plaques that may itch. They usually occurs in the mouth, and can ulcerate.
      • Why do they appear purple?

• The condition is associated with some edema (fluid due to the Tyndall effect appears blue) which appears blue, combined with red from dilated BVs, gives a purple color.

• Lesions also have white lines, known as Wickham’s striae  running through them.

• Histologically
  • The dermal-epidermal junction is disrupted. Bullae do not form. There are areas of hyperkeratosis and hypergranulosis (seen in the x-section of Wickham’s striae.

• Erythema Multiforme
  • Usually a reaction to a drug (example sulfas) or presence of a viral infection such as herpes leads to lesions called erythema multiforme
  • Manifests itself with multiple types of lesions such as macules, papules, and vesicles,
  • Characteristically associated with a bull’s eye lesion.
    • Caused by a substance toxic to keratinocytes (thought to be an inflammatory mediator or cytokine)
    • When it gets through to the epidermis, it causes necrosis (a gray area), which in turn leads to more inflammation (redness), which lets more toxin to the area, forming another band of necrosis (gray) and so on. This causes a bulls eye like lesion.

    
     

  • Severe erythema multiforme is known as Stevens-Johnson Syndrome, which is fatal up to 50% of the time. Thus, if you recognize this reaction, take your patient off the appropriate drug ASAP.
    • What’s so bad about Stevens-Johnson Syndrome?
      • This complication (he was very foggy about this and the recording didn’t clear it up) involves toxic epidermal necrolysis (basically, large amounts of the skin become necrotic real fast)
      • Important to rule out Staphylococcal Scalded Skin Syndrome or Ritter’s disease in infants, because they present in much the same way.
• Acanthosis Nigricans
  • Diffuse papillary lesion occurring mostly in skin folds (neck, axilla, popliteal fossa)
  • Basically, a furry, velvety, outgrowth of skin.
  • Histologically it is a papillomatosis and is NOT acanthotic nor hyperpigmented.
  • Seen in obese people
  • May be familial (autosomal dominant)
  • May be a paraneoplastic phenomenon associated strongly with gastric cancer.

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