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The complaint of rash as the presenting symptom in the outpatient setting is relatively common. A large survey of outpatient visits listed “rash” as the presenting symptom in 5% of all clinical encounters. Though “rash” is the presenting complaint rash verbalized by the patient, henceforth, “eruption” will be the preferred term in this text. The complaint of “rash” simply implies a widespread or localized eruption of similar primary or secondary skin lesions with an acute or gradual onset. This is in contrast to a patient presenting with a complaint of a “worrisome skin lesion(s)” which implies a benign or malignant neoplasm.  Eruptions are often accompanied by symptoms of itching (pruritus), burning, stinging, and/or irritation.  Therefore, eruptions can be disabling and interfere with concentration, sleep, and interactions with significant others and colleagues. Diagnosing the type and etiology of eruptions is an important training problem for third and fourth year medical students because accurate diagnosis requires enhanced visual and tactile skills along with accurate use of the vocabulary of dermatology. Finally, eruptions may provide clues to potentially life-threatening internal disease.



Describe and discuss

  • external anatomy and physiology of the skin and adnexal structures (hair, sweat glands)
  • pathophysiology of the following broad topics as they relate to the skin: acute inflammation, chronic inflammation, hypersensitivity reactions (type I, IV), Th1 & Th2 predominant immune reactions, heme synthesis pathways, itch sensory pathways
  • microbial pathogens associated with skin manifestations


  • ability to perform a complete medical history
  • ability to perform a skin-directed physical exam with a working knowledge of the vocabulary of dermatology
  • basic communication skills


Apply Medical Knowledge in the Clinical Encounter

1.     Describe the essential physical features of the primary skin lesions:

  • papule
  • nodule
  • mass
  • macule
  • patch (including erythroderma)
  • vesicle
  • bulla
  • urticaria
  • pustule
  • furuncle
  • cyst
  • plaque (occasionally listed as a secondary lesion)

2.     Describe the essential physical feature of the secondary skin lesions

  • scale
  • crust
  • erosion
  • ulceration
  • lichenification
  • excoriation

3.     Describe the approach to describing skin findings in a concise form:

  • location
  • color
  • size
  • secondary changes
  • primary lesion
  • configuration
  • distribution

4.     Describe the approach to diagnosing eruptions based on the hierarchy:

  • primary lesion
  • secondary changes
  • configuration
  • distribution (as opposed to focusing on the distribution first and primary lesion last)

5.     Describe the board categories of eruptions based on primary lesion:

  • papulosquamous (red scaly eruptions including macular, morbilliform, papular)
  • vesicular
  • urticarial
  • pustular

6.     Describe several common diagnoses and the typical presenting features of the eruptions from each of the board categories including:

  • psoriasis
  • seborrheic dermatitis
  • eczema
  • morbilliform drug eruption
  • contact dermatitis
  • syphilis
  • tinea corporis
  • lichen planus
  • bullous pemphigoid
  • pemphigus vulgaris
  • herpes zoster
  • urticaria
  • erythema multiforme
  • folliculitis



1.     Obtain, document, and present an age-appropriate medical history that differentiates among etiologies of disease, including:

  • eliciting a full description of symptoms
  • determining if the rash is associated with sexual activity
  • determining the patient’s risk for veneral disease
  • obtaining a description of all prior episodes of rash and how they were treated
  • determining the presence or absence of predisposing causes

2.     Distinguish all of the primary skin lesions on physical exam or clinical photograph.

3.     Describe skin findings in a concise logical form.

4.     Generate a meaningful differential diagnosis based on the skin findings focusing on the primary lesion.

5.     Use tactile sensations to assist in differentiating primary from secondary lesions.

6.     Recommend when to order diagnostic and laboratory tests, both prior to and after initiating treatment, based on the differential diagnosis, justify ordering them, and interpreting the results.

7.     Perform basic procedural skills.

8.     Identify the patient’s problem from all of the problems listed in the differential diagnosis by combining scientific knowledge, information obtained in the clinical encounter and collective experience with similar patients.

9.     Communicate the diagnosis to the patient.

10.  Record, present, research, critique, and manage clinical information.


Develop a Management Plan

Make decisions about what to include from the following items and explain why each item selected should be included:

1.     Discuss preventive measures, including counseling and educating patients about sexual activity.

2.     Consider treatment measures such as the appropriate prescribing of topical and oral medications as well as appropriate use of consultants and referral to specialists.

3.     Refer for psychological support if indicated.

4.     Access and utilize appropriate information systems to ascertain information about health system and community resources.

5.     Plan for follow-up.

6.     Formulate a prognosis and communicate it to the patient in a caring and compassionate manner.

7.     Communicate the treatment plan and follow-up plan to patient.

8.     Consider the cost-effectiveness of the management plan.


Differential Diagnosis


  • cellulitis
  • folliculitis
  • herpes zoster
  • impetigo
  • meningococcemia
  • Rocky Mountain spotted fever
  • secondary syphilis
  • tinea corporis
  • varicella


  • atopic eczema
  • bullous pemphigoid
  • buttate psoriasis
  • lichen planus
  • nummular eczema
  • pemphigus vulgaris
  • pityriasis rosea
  • psoriasis vulgaris
  • seborrheic dermatitis
  • systemic lupus erythematosus


  • allergic contact dermatitis
  • erythema multiforme
  • morbilliform drug eruptions
  • urticaria


  • mycosis fungoides
  • squamous cell
  • melanoma
  • basal cell