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Abnormal Foundations of Dermatology

CPR APPLICATIONS FOUNDATION · CHAPTER 19 · ABNORMAL

Abnormal Foundations of Dermatology

Organize the chapter before drilling into individual CPR concepts.

Supplemental foundation map: this page orients the detailed CPR Applications for Chapter 19. It is not part of the canonical CPR object inventory.

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19.8 · SOURCE CPR FOUNDATION

Concept

Abnormal dermatology is sorted by layer, morphology, distribution, symptom, and systemic danger. Inflammatory, infectious, autoimmune, vascular, malignant, nutritional, and drug-related skin disease can look similar until the lesion is described carefully. The safest move is to recognize morphology first and danger signs early.

Pattern

Step 1 gives pruritus, pain, scale, vesicles, bullae, purpura, ulceration, fever, mucosal involvement, rapid progression, or lesion evolution. Pruritus without systemic toxicity often supports inflammatory disease. Pain out of proportion, mucosal sloughing, hypotension, or nonblanching purpura changes urgency.

Rule

  1. Use morphology and distribution before disease name. Rash descriptions are diagnostic instructions.
  2. Use symptoms to refine. Itchy, painful, numb, tender, or rapidly spreading lesions mean different processes.
  3. Escalate systemic or mucosal disease. Fever, shock, mucosal involvement, purpura, or necrosis are danger signs.

Applications

  • Flexural pruritic rash child asthma → atopic dermatitis
  • Extensor plaques silvery scale → psoriasis
  • Tense bullae older adult → bullous pemphigoid
  • Pearly papule central ulcer → basal cell carcinoma
  • Pigmented lesion evolving asymmetrically → melanoma concern
  • Rapidly progressive erythema with severe pain out of proportion, systemic toxicity, or bullae → urgent evaluation for necrotizing soft-tissue infection
  • Tip: The dangerous rash is often defined by systemic signs

CPR APPLICATIONS · ACTIVE REASONING

Distinguish morphology from skin emergencies

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Decision 1: A patient has well-demarcated erythematous plaques with silvery scale on the elbows and knees. Which underlying process is most compatible?

Reveal the worked answer and changed-variable challenge

Best answer: Immune-mediated keratinocyte hyperproliferation characteristic of psoriasis. Psoriatic inflammation increases epidermal turnover and yields characteristic extensor plaques and scaling.

Transfer: How would flexural involvement with prominent pruritus and atopic history change the differential?

Decision 2: A patient has rapidly expanding erythema, extreme pain disproportionate to exam, fever, and systemic instability. What is the priority?

Reveal the worked answer and changed-variable challenge

Best answer: Urgent evaluation for necrotizing soft-tissue infection and possible surgical management. Disproportionate pain, progression, and systemic toxicity are red flags; rapid assessment and source control can be time-critical.

Transfer: Why might a seemingly limited superficial erythema be misleading early in a deep infection?

Decision 3: A pigmented lesion has changed in shape and color over several months. Which next reasoning step is best?

Reveal the worked answer and changed-variable challenge

Best answer: Evaluate for melanoma and other causes, with timely dermatologic assessment and biopsy when indicated. Evolution and asymmetry increase suspicion; ABCDE findings prompt evaluation but do not themselves establish histology.

Transfer: How would a new asymmetric lesion that differs from the patient’s other nevi affect concern?

Change the mechanism

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  • Chronic silvery extensor plaques: Psoriasis becomes a leading inflammatory mechanism.
  • Rapid progression with severe pain and toxicity: A necrotizing infection must be considered urgently.
  • Changing pigmented lesion: Assess ABCDE evolution and obtain appropriate clinical evaluation; morphology alone is not diagnosis.

Explain it back: Identify the mechanism, name the most important competing explanation, and predict what changes when the context shifts.

Unscored educational reasoning. Not a validated assessment or individualized clinical recommendation.

How to use this foundation map

  1. Identify the organizing mechanism.
  2. Recognize the pattern.
  3. Restate the rule without looking.
  4. Test transfer with applications and question practice.

Pair CPR with the 5P Approach™ when solving cases and questions.

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