Rosen & Barkin's 5-Minute Emergency Medicine Consult (597 page)

Chemical Weapons Poisoning

CODES

• 508.0 Acute pulmonary manifestations due to radiation
  
• 990 Effects of radiation, unspecified
  
• V87.39 Contact with and (suspected) exposure to other potentially hazardous substances
  

BASICS

• Morphology, distribution, associated systemic symptoms, and the evolution of a rash are important clinical considerations in identifying a dermatologic emergency
  
• Presentations of erythroderma, blistering/desquamation, purpura, and skin pain with systemic symptoms are warning signs of a potential emergency
  
• Abnormal skin lesions due to an inflammatory reaction that can be classified into patterns with distinctive clinical features
  
• 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
    
• Nodules:
  
  • Secondary to prolonged inflammatory response, cyst, or infiltrative process
    
  • Granulomatous lesions:
    
    • “Apple jelly” appearance when pressed with glass slide
      

• 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 chapter on 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
      
  • Diffuse:
    
    • Staphylococcal scalded skin syndrome
      
    • Toxic shock syndrome
      
    • Drug-induced, including drug reaction with eosinophilia and systemic symptoms (DRESS)
      
    • Viral exanthema
      
• 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
      
  • Urticaria:
    
    • Allergic reaction from drugs, food, infection, pressure, heat, or cold
      
• 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
    

DIAGNOSIS

• Age of patient
  
• Immune status (HIV, chemotherapy, diabetes, steroids)
  
• Chronologic and physical evolution
  
• Previous episodes/prior history of lesions/reactions
  
• Associated symptoms:
  
  • Pruritus
    
  • Fever
    
  • Abdominal pain
    
  • Myalgias/arthralgias
    
• Prodromal symptoms:
  
  • Fever
    
  • Headache
    
  • Cough
    
  • Odynophagia
    
  • Rhinorrhea
    
• Environmental exposure:
  
  • Tick bite
    
  • Unusual flora
    
  • Diet
    
  • Travel
    
  • Physical trauma (cold, heat, sun)
    
• Sick contacts
  
• Recent change in medication
  
• Family history
  

• Associated signs/symptoms:
  
  • Fever with infection/drug reaction/systemic inflammatory response
    
  • Skin pain out of proportion to the clinical picture is a worrisome sign of possible impending skin necrosis
    
  • Lymphadenopathy may be a symptom of DRESS
    
  • Pruritus associated with allergic reactions, systemic and contact
    
• Assess severity of systemic signs:
  
  • Abnormal vital signs, respiratory distress, hemodynamic instability
    
• Primary lesion appearance:
  
  • Vesicles:
    
    • Small, raised, clear fluid-filled lesions (<5 mm)
      
  • Bullae:
    
    • Large, raised, clear fluid-filled lesions (>5 mm)
      
  • Macule:
    
    • Nonraised areas of distinct coloration
      
  • Papule:
    
    • Raised, palpable lesions <5 mm in diameter, not fluid-filled
      
  • Pustules:
    
    • As vesicles and bullae, but containing purulent fluid
      
  • Nodule:
    
    • Solid, raised lesion >5 mm seated in deeper layer of skin and tissue
      
• Distribution of the rash:
  
  • Characterized as central/peripheral, confluent/scattered, mucosal/nonmucosal, presence of palm/sole involvement
    
• Secondary changes:
  
  • Scaling, lichenification, excoriation, fissuring all result from manipulation/scratching or proliferation/shedding of epidermal cells.
    
  • Erosions/ulcers from varying degrees of tissue loss due to loss of vascular supply/tissue integrity
    

• Identify systemic illness.
  
• Signs/symptoms of local infectious source
  
• Categorize the lesion morphology and distribution
  

• Presence of fever, systemic symptoms, or possible infection warrants blood work:
  
  • CBC with differential, electrolytes, BUN/creatinine
    
  • Blood cultures, viral cultures
    
  • Gram stain and culture of purulent lesions
    
  • Polymerase chain reaction (PCR) or Direct fluorescent antibody (DFA) of suspected viral lesions
    
• Rapid plasma reagin (RPR) or fluorescent treponemal antibody (FTA) for suspected syphilis
  
• Suspected autoimmune disorders:
  
  • CBC
    
  • ESR, CRP
    
  • Particular assays in consultation with a rheumatologist (ANA, antineutrophil cytoplasmic antibody)
    
• Petechiae/purpura:
  
  • CBC with platelets
    
  • Partial thromboplastin time, prothrombin time, INR
    
  • DIC screen: Fibrinogen, fibrin split products, haptoglobin, LDH
    
  • Urinalysis for suspected renal involvement in vasculitis
    

• In febrile and seriously ill patients, suspected septic lesions may be incised and drained and sent for cultures.
  
• Nikolsky test: Expansion of bullous lesion with lateral stress at margin indicates epidermal/dermal disruptive process
  
• Scrapings: Indicated to rule out topical fungal infections and parasites:
  
  • Potassium hydroxide preparation from edge of lesion reveal hyphae
    
  • Plain mineral oil to rule out scabies in pruritic linear lesions of hands
    
• Biopsy under dermatologic consultation to differentiate allergic/autoimmune/infectious processes