Vascular Pattern Reactions

 1.  Urticaria (hives)

• Antigenic causes:  can be due to drugs, infections or an antoimmune disorder
• Characterisitics
  • Wheels appear on the skin that can come and go in minutes or hours (if it is due to vasculitis then the wheels will persist)
  • They are sharply demarcated and can come together to form a serpinginous or gyrate form
  • The skin may appear dimpled due to the hair follicles anchoring the skin down

2.  Leukocyoclastic vasculitis

• Due to an antigen that can be from an infectious agent, ingestant or a paraprotein
• May reflect an underlying systemic disorder
• Characteristics:
  • Palpable purpura
  • Endothelial cells gaps will be filled with circulating immune complexes and complement
  • Involves the skin, kidney and gut (generally if it is on the skin its definitely in the gut)

3. Erythema Muliforme

• Causes are the same as urticaria (antigens due to drugs, infection or an autoimmune disorder)
• Characteristics: 
  • Target lesions:  3 rings (one is red, one is lighter and the middle is a dusky bull’s eye)
  • Papules and plaques that are flat topped
• You have to look for mucosal involvement

4. Bullous Erythema Multiforme

• Distributed across the trunk, palms, soles lips and other mucosal areas (gut)
• Most common cause is Herpes Simplex
• Characteristics
  • Tense blisters that have a red base
  • Targetoid lesions (there are blisters in the center of what looks like a target)
  • Erosive mucosal lesions that come with fever and toxicity (severe forms are stevens-Johnson syndrome (rmember that sulfonamides can cause that))
    • If there are erosive lesions around the mouth then they are also in the gut which can cause severe toxicity and death
  • Vascular reactions

5.  Erythema Nodosum

• Distribution is anterior legs and occasionally the palms
• Charcteristics
  • Very painful symmetrical red nodules (the patient will have a positive Chandelier sign which means they jump off the table when you touch it)
  • May have diarrhea
  • The nodules will involute in weeks and take on a bruise-like appearance
• Need to do a biopsy of the area to rule out other diseases (like Rocky Mountain Spotted)
  • Will see septal pannicultis
• Causes:
  • Streptococcal pharyngitis, Yersinia (in Europe)
  • Histoplasmosis, coccidiomyosis, mycobacteria
  • Sarcoidosis: bilateral hilar adenopathy
  • Regional enteritis or ulcerative colitis
  • Drugs: sulfas and oral contracenptives

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