Rosen & Barkin's 5-Minute Emergency Medicine Consult (458 page)

• WBC with differential:
  
  • Typically a modest elevation in total WBC between 10,000 and 20,000, which peaks during week 2 of the illness but occasionally can be 30,000–50,000
    
• Lymphocyte count—findings suggestive of IM:
  
  • >50% lymphocytes on differential
    
  • Absolute lymphocyte count >4,500
    
  • Elevated lymphocyte count with >10% atypical lymphocytes (up to 90% of patients)
    
• Liver function tests:
  
  • Elevated with transaminases up to 3 times normal found in 80–85% of patients in the 1st 2 wk
    
  • Significant elevations in bilirubin to the point of causing clinical jaundice in ∼5% of cases
    
• Monospot test detects presence of heterophile antibodies:
  
  • Moderately sensitive (85%) and highly specific (practically 100%)
    
  • Rarely false positives can occur with CMV, leukemia, lymphoma, rubella, hepatitis, HIV, or lupus
    
  • Most patients develop heterophile antibodies after ∼1 wk of illness
    
  • Small percentage of patients (<10%) never develop heterophile antibodies
    
  • Heterophile antibodies peak at 2–5 wk and may persist for several months
    
  • Positive test relates to a titer >1:40
    
  • Results likely to be negative in children <4 yr old
    
• Testing does exist for EBV-specific antibodies but is expensive, time consuming, and rarely needed
  
  • Useful in patients with atypical/severe cases or when monospot testing is negative and confirmation of IM is desired
    
  • Acute infection is indicated by antibodies (IgG, IgM) against viral capsid antigens (VCAs) without antibodies against the Epstein–Barr nuclear antigen (EBNA) which are only present during the latency period 3–4 wk after onset of illness
    
  • Past infection indicated by negative IgM and positive EBNA
    

Sonography or CT scan of abdomen for significant abdominal pain to identify splenic rupture and to ensure no signs of appendicitis

Divided into infectious and noninfectious causes:

• Infectious:
  
  • Adenovirus
    
  • CMV
    
  • Streptococcal pharyngitis
    
  • HIV
    
  • Rubella
    
  • Hepatitis A, B, C
    
  • Diphtheria in nonimmunized populations
    
  • Mumps
    
  • Toxoplasmosis
    
• Noninfectious:
  
  • Leukemia
    
  • Lymphoma
    
  • Medication-induced syndrome—phenytoin, sulfa drugs
    

TREATMENT

• ABC management. Airway edema may require intervention
  
• If possible, avoid placing patient in the same general area as post-transplant and other immunocompromised patients
  

• Supportive therapy:
  
  • Hydration with IV or PO fluids
    
  • Antipyretics for fever control
    
  • Analgesics for pain of sore throat
    
• Steroids (methylprednisolone, prednisone, or dexamethasone) if there is significant pharyngeal/tonsillar edema with concern about impending airway obstruction. May also be considered for massive splenomegaly, myocarditis, hemolytic anemia, or HLH. Treatment is controversial and theoretically may be associated with increased risk of secondary infections or malignant disease
  
• Antiviral therapy has not been proven to effect clinical course but emerging research may suggest potential benefits
  
• Antibiotics if concerned for bacterial superinfection:
  
  • Avoid ampicillin because of associated rash
    
• Counsel patient on athletic activity limitations (
  see
  follow-up recommendations)
  

Advise parents of athletic activity limitations (
see
follow-up recommendations)

• Methylprednisolone: 125 mg IV (peds: 2 mg/kg IV up to adult dose)
  
• Prednisone: 20–40 mg PO daily for 7 days (peds: 1 mg/kg up to adult dose) with subsequent tapering
  
• Dexamethasone: 12–16 mg PO (peds: 0.3 mg/kg up to adult dose)
  

FOLLOW-UP

• Significant airway edema that represents any level of potential airway compromise
  
• Neurologic or severe hematologic/hepatic complications
  
• Inability to take PO
  
• Pain control
  

• No airway compromise
  
• Mild hematologic complications or mild hepatitis
  
• Ability to take PO fluids
  
• Fever usually resolved within 10 days and lymph nodes and spleen within 4 wk; fatigue may continue for several weeks, although it may go on for 2–3 mo
  

• Infectious disease consultation may be useful if serology is not conclusive
  
• Significant complications or persistent symptoms
  

• Contact sports, physical education, or other strenuous exercise should be avoided in the 1st 3 wk regardless of spleen size or current symptoms.
  
• After the initial 3-wk period patients need repeat outpatient evaluation to determine if they are able to return to full activity. Those with concerns of persistent symptoms including splenomegaly may require further studies (i.e., ultrasound) to determine when they are safe to return to full activity
  

• Although usually self-limited, significant complications occur and require consultation
  
• Treatment with steroids may be useful but is controversial due to potential increased risk of complications
  

• American Academy of Pediatrics.
  Red Book: 2013 Report of the Committee on Infectious Disease.
  29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012.
  
• Auwaerter PG. Recent advances in the understanding of infectious mononucleosis: Are prospects improved for treatment or control?
  Expert Rev Anti Infect Ther
  . 2006;4:1039–1049.
  
• Fafi-Kremer S, Morand P, Brion JP, et al. Long-term shedding of infectious Epstein-Barr virus after infectious mononucleosis.
  J Infect Dis
  . 2005;191(6):985–989.
  
• Higgins CD, Swerdlow AJ, Macsween KF, et al. A study of risk factors for acquisition of Epstein-Barr virus and its subtypes.
  J Infect Dis
  . 2007;195:474–482.
  
• Hurt C, Tammaro D. Diagnostic evaluation of mononucleosis-like illness.
  Am J Med
  . 2007;120:911.
  
• Luzuriaga K, Sullivan JL. Infectious mononucleosis.
  N Engl J Med
  . 2010;362:1993–2000.
  
• Putukian M, O’Connor F, Stricker P, et al. Mononucleosis and athletic participation: An evidence-based subject review.
  Clin J Sport Med.
  2008;18(4):309–315.
  

CODES

075 Infectious mononucleosis

BASICS

• Methicillin-resistant
  Staphylococcus aureus
  (MRSA) has historically been a pathogen endemic within healthcare settings, usually affecting the elderly and chronically ill. This strain of
  S. aureus
  has been termed “healthcare-associated MRSA” (HA-MRSA).
  
• Throughout the past decade, MRSA has become an increasingly common pathogen among younger, healthier populations who do not have a healthcare-related exposure history. This type of MRSA pathogen has been termed “community-acquired MRSA” (CA-MRSA).
  
• CA-MRSA is the most common cause of skin and soft tissue infections seen in the ED
  
• While CA-MRSA may cause skin and soft tissue infection, it may also lead to severe multisystem disease, including sepsis and necrotizing pneumonia
  

HA-MRSA (see below) is a different genotypic form of MRSA that frequently causes morbidity among the elderly, especially those living within extended-care facilities or those with healthcare-related exposures.

• S. aureus
  is a gram-positive cocci frequently colonizing the skin
  
• MRSA refers to a specific strain of
  S. aureus
  that has resistance against the antimicrobial properties of numerous antibiotics, including methicillin
  
• Prisoners, athletes, soldiers, children in daycare, IV drug users, and those with prior treatment for MRSA or exposure to MRSA are at highest risk for colonization and subsequent infection.
  

DIAGNOSIS