Rash

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Basics

Description

  • Use appropriate terminology to categorize the unknown rash:
    • Basic morphology:
      • Diameter
      • Flat or elevated
      • Solid or fluid filled
    • Color:
      • Hyperpigmented
      • Hypopigmented
      • Erythematous
    • Shape:
      • Discoid
      • Oval
      • Annular
      • Arcuate
      • Targetoid
    • Distribution:
      • Peripheral vs. central
      • Symmetrical
      • Discrete (separated from one another)
      • Linear
      • Dermatomal
      • Serpiginous
      • Reticular
      • Grouped
      • Photodistributed
    • Associated symptoms:
      • Itch
      • Pain
      • Tenderness
      • Burning
      • Systemic symptoms
    • Evolution of the rash:
      • Onset and duration
      • Severity and flares
  • Morphology:
    • Vesiculobullous lesions:
      • Fluid-filled swelling of the skin or sloughing due to disruption of epidermal/dermal integrity
    • Purpura and petechiae:
      • Failure of normal vascular integrity/hemostatic mechanisms
      • Do not blanch on palpation
    • Erythema:
      • Erythroderma when covering ≥90% of the skin surface
      • Vascular dilatation of the superficial vessels leading to red macular lesions
      • Blanches on palpation
    • Figurate erythema:
      • Erythema classified by its particular annular or arcuate shape
    • Papulosquamous:
      • Papules and scaly desquamation of the skin
      • Lesions may also be red and macular
      • Classified into psoriasiform, pityriasiform, lichenoid, annular, and eczematous
    • Granulomatous lesions:
      • Infiltrated papules and plaques, lack of scales
      • “Apple jelly” appearance when pressed with glass slide
    • Nodules:
      • Secondary to prolonged inflammatory response, cyst, or infiltrative process
  • Warning signs of a potential emergency condition:
    • Erythroderma
    • Blistering/desquamation
    • Purpura
    • Skin pain with systemic symptoms
Etiology/Differential Diagnoses
  • Vesiculobullous lesions:
    • Toxic epidermal necrolysis (mucosal and >30% body surface area involvement)
    • Stevens–Johnson syndrome (mucosal and ≤10% body surface area involvement)
    • Pemphigus vulgaris
    • Bullous pemphigoid
    • Disseminated herpes simplex
    • Herpes zoster
    • Varicella
    • Smallpox
    • Vaccinia
    • Allergic contact dermatitis
  • Purpura and petechiae:
    • Meningococcemia
    • Gonococcemia
    • Purpura fulminans/disseminated intravascular coagulopathy (DIC)
    • Rocky Mountain spotted fever (RMSF):
      • Pronounced prodrome of fever, headache, myalgia, rash, peripheral moves to palms/soles
    • Ecthyma gangrenosum:
      • Pseudomonas infections in critically ill and immunocompromised patients
    • Babesiosis: Similar to RMSF, rash less often, frequent coinfection with Lyme
    • Vasculitis
    • Multiple systemic illnesses (see “Purpura”)
  • Erythroderma:
    • Toxic shock syndrome
    • Drug-induced
    • Psoriasis
    • Seborrheic dermatitis
    • Mycosis fungoides
    • Lymphoma of the skin
  • Erythematous rashes:
    • Localized:
      • Cellulitis
      • Early necrotizing fasciitis with concomitant skin pain
      • Urticaria
    • Diffuse:
      • Staphylococcal scalded skin syndrome
      • Toxic shock syndrome
      • Drug-induced, including drug reaction with eosinophilia and systemic symptoms (DRESS)
      • Viral exanthema
      • Allergic reaction from drugs, food, infection, pressure, heat, or cold
  • Figurate erythema:
    • Erythema chronicum migrans (large red ring that arises around a tick bite):
      • Lyme disease
    • Erythema multiforme:
      • Mycoplasma pneumoniae
      • Herpes simplex
      • Drug reaction leading to Steven–Johnson syndrome
  • Papulosquamous:
    • Psoriasiform:
      • Psoriasis
      • Seborrheic dermatitis
      • Drug-induced
    • Pityriasiform:
      • Pityriasis rosea
      • Secondary syphilis
      • Tinea versicolor
    • Lichenoid:
      • Lichen planus
      • Drug-induced
    • Annular:
      • Tinea
      • Figurate erythema (see below)
    • Eczematous:
      • Atopic dermatitis
      • Allergic contact dermatitis
      • Irritant dermatitis
  • Nodules:
    • Granulomatous disease:
      • Sarcoid
      • Granuloma annulare
      • Infectious: Leprosy, tuberculosis, deep fungal infection
    • Panniculitis:
      • Erythema nodosum
    • Lymphoma of the skin
    • Cysts
    • Tumors and metastatic disease

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Basics

Description

  • Use appropriate terminology to categorize the unknown rash:
    • Basic morphology:
      • Diameter
      • Flat or elevated
      • Solid or fluid filled
    • Color:
      • Hyperpigmented
      • Hypopigmented
      • Erythematous
    • Shape:
      • Discoid
      • Oval
      • Annular
      • Arcuate
      • Targetoid
    • Distribution:
      • Peripheral vs. central
      • Symmetrical
      • Discrete (separated from one another)
      • Linear
      • Dermatomal
      • Serpiginous
      • Reticular
      • Grouped
      • Photodistributed
    • Associated symptoms:
      • Itch
      • Pain
      • Tenderness
      • Burning
      • Systemic symptoms
    • Evolution of the rash:
      • Onset and duration
      • Severity and flares
  • Morphology:
    • Vesiculobullous lesions:
      • Fluid-filled swelling of the skin or sloughing due to disruption of epidermal/dermal integrity
    • Purpura and petechiae:
      • Failure of normal vascular integrity/hemostatic mechanisms
      • Do not blanch on palpation
    • Erythema:
      • Erythroderma when covering ≥90% of the skin surface
      • Vascular dilatation of the superficial vessels leading to red macular lesions
      • Blanches on palpation
    • Figurate erythema:
      • Erythema classified by its particular annular or arcuate shape
    • Papulosquamous:
      • Papules and scaly desquamation of the skin
      • Lesions may also be red and macular
      • Classified into psoriasiform, pityriasiform, lichenoid, annular, and eczematous
    • Granulomatous lesions:
      • Infiltrated papules and plaques, lack of scales
      • “Apple jelly” appearance when pressed with glass slide
    • Nodules:
      • Secondary to prolonged inflammatory response, cyst, or infiltrative process
  • Warning signs of a potential emergency condition:
    • Erythroderma
    • Blistering/desquamation
    • Purpura
    • Skin pain with systemic symptoms
Etiology/Differential Diagnoses
  • Vesiculobullous lesions:
    • Toxic epidermal necrolysis (mucosal and >30% body surface area involvement)
    • Stevens–Johnson syndrome (mucosal and ≤10% body surface area involvement)
    • Pemphigus vulgaris
    • Bullous pemphigoid
    • Disseminated herpes simplex
    • Herpes zoster
    • Varicella
    • Smallpox
    • Vaccinia
    • Allergic contact dermatitis
  • Purpura and petechiae:
    • Meningococcemia
    • Gonococcemia
    • Purpura fulminans/disseminated intravascular coagulopathy (DIC)
    • Rocky Mountain spotted fever (RMSF):
      • Pronounced prodrome of fever, headache, myalgia, rash, peripheral moves to palms/soles
    • Ecthyma gangrenosum:
      • Pseudomonas infections in critically ill and immunocompromised patients
    • Babesiosis: Similar to RMSF, rash less often, frequent coinfection with Lyme
    • Vasculitis
    • Multiple systemic illnesses (see “Purpura”)
  • Erythroderma:
    • Toxic shock syndrome
    • Drug-induced
    • Psoriasis
    • Seborrheic dermatitis
    • Mycosis fungoides
    • Lymphoma of the skin
  • Erythematous rashes:
    • Localized:
      • Cellulitis
      • Early necrotizing fasciitis with concomitant skin pain
      • Urticaria
    • Diffuse:
      • Staphylococcal scalded skin syndrome
      • Toxic shock syndrome
      • Drug-induced, including drug reaction with eosinophilia and systemic symptoms (DRESS)
      • Viral exanthema
      • Allergic reaction from drugs, food, infection, pressure, heat, or cold
  • Figurate erythema:
    • Erythema chronicum migrans (large red ring that arises around a tick bite):
      • Lyme disease
    • Erythema multiforme:
      • Mycoplasma pneumoniae
      • Herpes simplex
      • Drug reaction leading to Steven–Johnson syndrome
  • Papulosquamous:
    • Psoriasiform:
      • Psoriasis
      • Seborrheic dermatitis
      • Drug-induced
    • Pityriasiform:
      • Pityriasis rosea
      • Secondary syphilis
      • Tinea versicolor
    • Lichenoid:
      • Lichen planus
      • Drug-induced
    • Annular:
      • Tinea
      • Figurate erythema (see below)
    • Eczematous:
      • Atopic dermatitis
      • Allergic contact dermatitis
      • Irritant dermatitis
  • Nodules:
    • Granulomatous disease:
      • Sarcoid
      • Granuloma annulare
      • Infectious: Leprosy, tuberculosis, deep fungal infection
    • Panniculitis:
      • Erythema nodosum
    • Lymphoma of the skin
    • Cysts
    • Tumors and metastatic disease

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