Rosen & Barkin's 5-Minute Emergency Medicine Consult (254 page)

• Acetaminophen: 500 mg (peds: 15 mg/kg/dose) PO q6h PRN fever for up to 5 days
  
  • Dose not to exceed 4 g/24h
    
• Diphenhydramine: 25 mg (peds: 1–2 mg/kg/dose) PO q6h PRN itching for up to 5 days
  
• Ibuprofen: 400 mg (peds: 10 mg/kg/dose) PO q8h PRN pain for up to 5 days
  
• IVIG only in consultation with ID specialist
  

FOLLOW-UP

• Aplastic crisis or severe anemia
  
• Severely immunocompromised
  
• Hydrops fetalis
  
• Toxic appearance
  
• Severe arthritis
  

• Nearly all patients
  
• Normal CBC, O
  ₂
  sat, and BP
  
• Patients are no longer contagious following appearance of facial rash and may return to day care, school, or work
  

• All patients without existing primary care physicians should be referred to a generalist for follow-up as needed
  
• Patients with hereditary anemias should be referred to hematology for follow-up in 1–2 days
  
• All immunocompromised patients require prompt subspecialty follow-up
  
• Pregnant patients with new infection should have immediate follow-up with OB/GYN for further monitoring and ultrasound
  

• Pregnant women with new parvovirus B19 infection may need serial ultrasounds for 10–12 wk.
  
• Patients at risk for aplastic crisis should follow-up with the appropriate specialties 1–2 days after ED discharge for repeat CBC
  

Prevention:

• No vaccine available
  
• Frequent handwashing helps prevent spread
  
• No current recommendations to keep children out of school, since most children are no longer contagious by the time the diagnosis is made.
  
• Pregnant women may choose to stay away from a workplace outbreak, but no current official recommendation exists
  

• Transient aplastic crisis in patients with anemias: Sickle cell disease, hereditary spherocytosis, thalassemia, iron-deficiency, or other conditions with shortened red cell lifespan:
  
  • Usually full recovery within 2 wk
    
• Persistent infection with severe anemia if immunocompromised and unable to mount antibody response, especially with HIV
  
• Arthritis or hypersensitivity dermatitis in adults:
  
  • May have transient rheumatoid factor positivity, but no true association with rheumatoid arthritis and no joint destruction
    
• Association with papular, purpuric gloves, and socks syndrome in adults:
  
  • Symmetric, painful progressive rash and edema of hands and feet
    
  • Erythema progresses to petechiae, purpura, and occasionally bullae
    
  • This syndrome is also associated with many other viruses and drugs
    
• Extremely rare – hepatosplenomegaly, heart failure, CVA, thrombocytopenia, leukopenia
  

• Risk of hydrops fetalis in pregnancy
  
• 60% of pregnant women are susceptible to new infection
  
• 30% risk of transplacental infection with new maternal infection
  
• Affects fetal liver (main site of erythropoiesis), leading to anemia, CHF, myocarditis, IUGR
  
• 2–6% risk of fetal loss, highest in 2nd trimester
  

• Parvovirus B19 is usually a self-limited, mild illness.
  
• Common symptoms include “slapped-cheeks” rash with subsequent diffuse lacy rash and arthropathy
  
• Patients are no longer contagious when the rash appears and aplastic crisis resolves
  
• Evaluate all patients with history of hereditary or iron-deficiency anemia for aplastic crisis
  
• Evaluate all patients with history of immunosuppression for chronic infection with persistent anemia
  
• Confirm diagnosis in all pregnant patients. If no proven immunity, monitor for fetal complications and refer for follow-up
  

• Servey JT, Reamy BV, Hodge J. Clinical presentations of parvovirus B19 infection.
  Am Fam Physician
  . 2007;75:373–376.
  
• Vafaie J, Schwartz RA. Erythema infectiosum.
  J Cutan Med Surg
  . 2005;9:159–161.
  
• Weir E. Parvovirus B19 infection: Fifth disease and more.
  CMAJ
  . 2005;172:743.
  

CODES

057.0 Erythema infectiosum (fifth disease)

BASICS

• A rash caused by a hypersensitivity reaction:
  
  • May occur in response to various medications, infections, or other illness
    
• Erythema multiforme (EM) minor:
  
  • Typical target lesions
    
  • Edematous papules
    
  • Usually distributed peripherally
    
  • Benign, self-limited rash generally not associated with acute, serious illness
    
• EM major
  
  • Also called bullous EM
    
  • Target lesions
    
  • Edematous papules
    
  • Also with peripheral distribution
    
  • Involves 1 or more mucous membranes
    
  • <10% total body surface area of epidermal detachment
    
• Differentiate from:
  
  • Stevens–Johnson syndrome (SJS):
    
    • Also <10% TBSA epidermal detachment
      
    • Often widespread blisters over trunk and face
      
    • Mucosal involvement
      
  • Toxic epidermal necrolysis (TEN)
    
    • >30% TBSA epidermal detachment
      
  • EM is now considered a different entity from SJS and EM
    
• Most often affects children and young adults (>50% younger than 20 yr)
  
• Males are affected more often than females.
  

• Hypersensitivity reaction, probably transient autoimmune defect
  
• Herpes simplex virus
  (HSV) is the most common precipitant (>70%).
  
• Other causes include:
  
  • Idiopathic
    
  • Medications
    
    • Penicillin
      
    • Sulfur based
      
    • Phenytoin
      
    • Barbiturates
      
    • NSAIDs
      
  • Vaccines
    
    • Diphtheria—tetanus
      
    • Hepatitis B
      
    • Smallpox
      
  • Malignancy
    
  • Infection
    
    • HIV
      
    • CMV
      
    • Hepatitis C
      
    • Mycoplasma infections
      

DIAGNOSIS

• Prodrome: Infrequent systemic symptoms (mild fever/malaise), antecedent HSV in most cases (within 3 wk)
  
• Usually not associated with severe systemic illness
  

Characteristic rash:

• Lesions:
  
  • Symmetric dull red macules and papules
    
  • Evolve into round, well-demarcated target lesions with central clearing
    
  • No epidermal necrosis
    with EM minor
    
• Multiforme
  refers to the evolution of the rash through various stages at different times.
  
• Distribution:
  
  • Extremities
    
  • Dorsal hands and feet
    
  • Extensor surfaces
    
  • Elbows and knees.
    
• 1 of the few rashes that may involve palms and soles
  
• Spread: From extremities toward trunk
  
• Mucosal involvement: Minor blistering or erosions of 1 mucosal surface (lips/mouth)
  
• Duration: Usually 1–4 wk, but may become chronic or recurrent
  

Complete history and physical exam, with special attention to the skin, genitourinary system, recent infectious symptoms, and recent medications

No specific lab tests needed

No specific imaging is helpful.

• Skin biopsy reveals mononuclear cell infiltrate around upper dermal blood vessels, without leukocytoclastic vasculitis and necrosis of epidermal keratinocytes.
  
• Biopsy is not necessary in most cases.
  

• Systemic lupus erythematosus
  
• Fixed drug eruption
  
• Pityriasis rosea
  
• Secondary syphilis
  
• Erythema migrans
  
• Urticaria
  
• SJS
  
• TEN
  
• Vasculitis
  
• Viral exanthem
  

TREATMENT