Dermatological Signs of Medical Emergencies

Introduction

In the context of a medical emergency, the skin is often the most accessible organ for rapid triage. The dermatologist's role is to recognize specific patterns that signal immediate life threat.

This chapter focuses on the recognition of "Red Flag" signs:

1. Skin Failure (Detachment/Erythroderma).
2. Vascular Failure (Purpura Fulminans/Vasculitis).
3. Soft Tissue Destruction (Necrotizing Fasciitis).

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13.1 Acute Skin Failure: Blistering and Detachment

The differential diagnosis of acute widespread blistering relies on three key parameters: level of split, mucosal involvement, and patient age.

13.1.1 Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN)

Pattern Recognition:

• Prodrome: "Flu-like" illness (fever, stinging eyes, odynophagia) precedes rash by 1-3 days.
• Primary Lesion: Dusky (violaceous), atypical targets or purpuric macules.
  • Differentiation: Typical targets (three zones) suggest Erythema Multiforme (EM). SJS/TEN targets are atypical (two zones, flat).
• Distribution: Starts on Face/Upper Trunk $\rightarrow$ Centrifugal spread.
• Key Signs:
  • Skin Pain: Tenderness to palpation is an early warning sign (indicates full-thickness necrosis).
  • Nikolsky Sign: Lateral pressure on erythematous skin causes epidermal detachment.
  • Asboe-Hansen Sign: Vertical pressure on a bulla extends it laterally.
• Mucosal Signs (>90% cases):
  • Hemorrhagic crusting of lips.
  • Painful stomatitis.
  • Genital/Anal erosions.
  • Purulent conjunctivitis.

13.1.2 Staphylococcal Scalded Skin Syndrome (SSSS)

Pattern Recognition:

• Population: Neonates/Infants (or adults with renal failure).
• Morphology: Diffuse "sunburn" erythema + Superficial wrinkling/peeling.
• Key Differentiation:
  • Mucosa is SPARED.
  • Focus of Infection: Look for impetigo, omphalitis, or purulent conjunctivitis (the toxin source).
  • Sad Man Facies: Radial crusting around mouth/eyes.

Diagnostic Algorithm: Acute Blistering Eruption

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13.1.3 Acute Generalized Exanthematous Pustulosis (AGEP)

Often confused with TEN because of superficial peeling.

• Primary Lesion: Hundreds of non-follicular sterile pustules on edematous erythema.
• Time Course: Rapid onset (<48 hours) after antibiotics.
• Location: Starts in folds (axillae, groin) and face.
• Differentiating Sign: Edema of the face/hands is common. Pustules are superificial. Mucosa usually spared.

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13.2 Purpura and Vascular Emergencies

Purpura implies extravasation of blood. The key distinction is Palpable (Inflammatory/Vasculitis) vs Non-Palpable (Thrombotic/Vascular).

13.2.1 Meningococcemia (Acute)

The Golden Hour Diagnosis.

• Early Sign: "Transient erythematous macules" (often overlooked).
• Warning Sign: Leg Pain and cold hands/feet (perfusional shock) often precede the rash.
• Cardinal Sign: Retiform Purpura.
  • Appearance: Geographic, angular, "map-like" purple patches with central black necrosis (eschar).
  • Mechanism: Microvascular thrombosis (not just vasculitis).
• Gunmetal Gray: A distinctive color of early necrotic lesions.

13.2.2 Purpura Fulminans

A syndrome of intravascular thrombosis and hemorrhagic infarction.

• Context: Post-infection (Varicella, Strep) or Protein C/S deficiency (neonates).
• Morphology: Large, ecchymotic areas rapidly progressing to gangrene.
• Distribution: Distal extremities or pressure sites.
• Differential:
  • Capnocytophaga canimorsus: History of Dog Bite (or lick) in asplenic/alcoholic patient.

13.2.3 Rocky Mountain Spotted Fever (RMSF)

• Triad: Fever + Headache + Rash.
• Rash Evolution:
  • Starts: Blanchable pink macules on Wrists and Ankles (day 2-4).
  • Spreads: Centripetally (Inward) to trunk. Palmar/Plantar involvement common.
  • Becomes: Petechial/Purpuric (late sign, poor prognosis).

Diagnostic Algorithm: Fellow's Guide to Purpura

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13.3 Soft Tissue Infections: "Hidden" Necrosis

13.3.1 Necrotizing Fasciitis

Infection of the deep fascia. The skin surface often underestimates the deep destruction.

"Hard Signs" (Late, specific):

1. Crepitus: Gas in tissue (palpable "Rice Krispies").
2. Bullae: Hemorrhagic blisters (indicates perforator vessel infarction).
3. Skin Anesthesia: Loss of focal sensation (nerve destruction).
4. Ecchymosis: Rapidly spreading bruising.

"Soft Signs" (Early, sensitive):

1. Pain out of proportion to erythema.
2. Indistinct Borders: Erythema that fades out (unlike the sharp step of Erysipela).
3. Wooden Induration: Tissue feels hard, not boggy.

13.3.2 Toxic Shock Syndrome (TSS)

• Staphylococcal TSS:
  • Source: Tampons, nasal packing, surgical wound.
  • Rash: Diffuse "sunburn" erythroderma (scarlatiniform) $\rightarrow$ Desquamation of palms/soles (1-2 weeks later).
  • Mucosa: Hyperemia ("Beefy red").
• Streptococcal TSS:
  • Source: Soft tissue infection (Nec Fasc).
  • Rash: Often localized to site of infection, may be absent.
  • Systemic: Hypotension, rapid organ failure.

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13.4 Erythroderma (Red Man Syndrome)

Definition: Erythema treating >90% BSA. Dermatologic Urgency: Risks of thermoregulatory failure, high-output cardiac failure, and sepsis.

Diagnostic Clues (The "Nose" of the Diagnosis):

1. Psoriasis: History of plaques. Look for Nail Pitting or Oil Spots. Look for spared "islands of normal skin" (Nappes claires).
2. Atopic Dermatitis: History of eczema. Lichenification (thickening). Intractable pruritus.
3. Drugs (Vancomycin, Allopurinol): Temporal relationship. Eosinophilia.
4. Sezary Syndrome (CTCL): Léonine facies (infiltrated brow), Keratoderma, Lymphadenopathy.

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13.5 Drug Reaction with Eosinophilia and Systemic Systems (DRESS)

A distinct entity from SJS/TEN.

• Timeline: Delayed. 2-6 weeks after starting drug.
• The Look:
  • Facial Edema: Characteristic initial sign (periorbital swelling).
  • Morbilliform Eruption: Often descends from face/neck. Becomes confluent/infiltrated.
• Systemic:
  • Lymphadenopathy: Generalized.
  • Fever: High, persistent.
  • Visceral: Hepatitis (90%), Nephritis.
• Differentiation from Exanthem: Facial edema, fever, lymphadenopathy, and eosinophilia distinguish DRESS from a simple drug rash.

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13.6 Diagnostic Considerations for the Febrile Traveler

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Summary Table: Emergent Signs