General approach to rashes

This page is for adult patients; for other age groups see pediatric rashes and neonatal rashes

Background

  • A wide range of benign and dangerous pathology can present with a rash

Rash Red Flags[1]

  • Fever
  • Toxic appearance
  • Hypotension
  • Mucosal lesions
  • Severe pain
  • Very old or young age
  • Immunosuppressed
  • New medication

Dermatology Nomenclature

Small lesions (<0.5cm)

  • Macule – flat, cirumscribed, colored, non palpable
  • Papule – raised, solid and palpable
  • Vesicle – raised, palpable, clear fluid-filled
  • Pustule – raised, palpable, pus filled (leukocytes or keratin)

Large lesions (>0.5cm)

  • Patch – large macule (flat non-palpable colored area)
  • Plaque – superficially raised, circumscribed solid area
  • Nodule – distinct large papule
  • Bulla - large vesicle (blisters if epidermal layer completely sloughed off)
  • Wheal – firm and edematous plaque (edema of the dermis)

Other

  • Plaque/scaley papule
  • Eschar
  • Erosion/ulcer
  • Purpura/petechia
  • Plaque/smooth papule

Clinical Features

History

  • Key elements from the history include:
    • Distribution and progression of the skin lesions
    • Recent exposures (sick contacts, foreign travel, sexual history and vaccination status)
    • Any new medications

Physical Exam

  • Pay specific attention to vital signs
    • A rash associated with fever or hypotension should make you worry about potentially deadly diagnoses
  • Perform a careful physical exam
    • Undressing the patient to fully examine the trunk and the extremities
    • Look at palms, soles and mucous membranes
    • Touch the skin with a gloved hand to determine if the lesions are flat or raised
    • Press on lesions to see whether they blanch
    • Rub erythematous skin to see if it sloughs

Differential Diagnosis

Rash

Vesiculobullous rashes

Febrile

Afebrile

Necrotizing rashes

Petechiae/Purpura (by cause)

Erythematous rash

Dark raised skin lesions

Evaluation

Algorithm for the Evaluation of Dermatologic Emergencies

Rash visual diagnosis

Erythematous rash

Vesiculobullous rashes visual diagnosis

Dark raised skin lesions

Management

  • Based on diagnosis

Disposition

  • Based on diagnosis

See Also

External Links

References

  1. Nguyen T and Freedman J. Dermatologic Emergencies: Diagnosing and Managing Life-Threatening Rashes. Emergency Medicine Practice. September 2002 volume 4 no 9.