Herpes Zoster

Aka: Herpes Zoster, Shingles

1. See Also
   1. Postherpetic Neuralgia
   2. Herpes Zoster Ophthalmicus
2. Epidemiology
   1. Incidence: 1 Million cases in United States annually
   2. Age: Peak onset at 50-79 years old
   3. Gender predominance: Women account for 60% of cases
3. Pathophysiology
   1. Reactivation of latent virus from dorsal root Ganglion
      1. Occurs in 10-20% of people previously exposed to Chicken Pox
   2. Inflammation to acute viral ID in segmental nerve
   3. Contagious to non-immune persons
      1. Avoid contact until rash heals
4. Risk Factors
   1. Age over 50 years old
   2. Chicken Pox at age <1 year old
   3. Altered cell-mediated immunity (especially if onset in a younger patient)
      1. HIV Infection
      2. Malignancy
      3. Organ transplant status
      4. Immunosuppressant use
5. Symptoms: Prodrome
   1. Timing
      1. May be precede rash by 1-5 days
   2. Most common symptoms
      1. Fever (variably present)
      2. Headache
      3. Photophobia
      4. Paresthesias
         1. Pain within dermatome occurs first
         2. Examples: itching, burning, hyperesthesia
      5. Malaise
6. Signs: Rash
   1. Timing
      1. Develops after 48-72 hours (up to 5 days before rash)
      2. Lesions crust and heal within 2-4 weeks
   2. Distribution
      1. Follows 1-2 dermatomes and rarely crossess the mid-line
      2. Back and face are most commonly affected
   3. Characteristics
      1. Starts as erythematous, maculopapular rash
      2. Clear Vesicles develop
      3. Vessicles turn cloudy within 3-5 days
   4. Associated Findings
      1. Tender regional lymph nodes
   5. Variants
      1. Zoster sine herpete (zoster without a rash)
         1. Zoster without rash is uncommon but does occur
      2. Hutchinson's sign (Vesicle on the tip of nose)
         1. Associated with Herpes Zoster Ophthalmicus
         2. Stain the eye for Fluorescein and observe for dendrites
         3. Exercise high level of suspicion for ocular involvement
      3. Ramsay Hunt Syndrome (Vesicle in ear)
         1. Associated with Bell's Palsy
         2. Course may be more prolonged
   6. Images
      1. 
      2. 
7. Labs: Vesicle fluid testing
   1. Zoster PCR
      1. Test Sensitivity: 95%
      2. Test Specificity: 99%
   2. Direct immunofluorescent antigen staining
      1. Test Sensitivity: 82%
      2. Test Specificity: 76%
   3. Virus Culture
      1. Test Sensitivity: 20%
      2. Test Specificity: 99%
   4. Tzanck Smear of lesion base (Multinucleated giant cells)
      1. Rarely performed now in United States
   5. References
      1. Sauerbrei (1999) J Clin Virol 14(1): 31-36
8. Differential Diagnosis
   1. Cellulitis
   2. Painful serious condition (prior to dermatitis appearance)
      1. Acute Abdomen
      2. Acute Coronary Syndrome
9. Complications
   1. Postherpetic Neuralgia
   2. Herpes Zoster Ophthalmicus
   3. Meningitis
   4. Encephalitis
   5. Granulomatous Angiitis with contralateral Hemiplegia
   6. Cutaneous dissemination in Lymphoma (40%)
   7. Diffuse involvement (including pneumonitis)
      1. Occurs in immunocompromised patients
10. Management: Antivirals
    1. Relative indications for antivirals (maximal benefit)
       1. Onset within 72 hours of starting treatment
       2. Facial involvement (due to associated risk of ocular involvement)
       3. Age 50 years and older
       4. More than 50 lesions
       5. Patients are likely to see benefit if still having active vessicle eruptions, even if delayed beyond the 72 hour window
    2. Oral antiviral agents
       1. Acyclovir
          1. Dose: 800 mg orally five times daily for 7-10 days
          2. Reduces healing time, pain, and rash dissemination
          3. Least expensive of all antiviral options by an order of magnitude
          4. Valacyclovir appeared more effective in over age 50
             1. (1999) Med Lett Drugs Ther 41:113-20
       2. Valacyclovir
          1. Dose: 1000 mg orally three times daily for 7 days
          2. Equivalent efficacy to Famciclovir
             1. Tyring (2000) Arch Fam Med 9:863-9
       3. Famciclovir
          1. Dose: 500 mg orally three times daily for 7 days
          2. Lesions healed faster, more brief virus shedding
          3. Reduces Postherpetic Neuralgia duration by 2 months
          4. Reference
             1. Tyring (1995) Ann Intern Med 123:89-96
11. Management: Pain Management
    1. Analgesics
       1. Schedule Analgesics around the clock (not prn)
       2. Mild to moderate pain
          1. Acetaminophen
          2. NSAIDs
       3. Moderate to severe pain
          1. Opioid Analgesics
       4. Refractory pain (agents used in Postherpetic Neuralgia)
          1. No evidence that these agents reduce acute Shingles pain or that they prevent Postherpetic Neuralgia
          2. Amitriptyline (Elavil)
          3. Gabapentin (Neurontin)
    2. Systemic Corticosteroids
       1. Use is controversial and not routinely recommended
       2. May be associated with increased complications (e.g. bacterial superinfection)
       3. May reduce acute pain, inflammation and speed up healing
       4. Does not reduce risk of Postherpetic Neuralgia
       5. References
          1. Wood (1994) N Engl J Med 330:896-900
12. Management: Special Circumstances
    1. Zoster Ophthalmicus
       1. See Herpes Zoster Ophthalmicus
    2. Immunocompromised Patient
       1. Acyclovir 10 mg/kg IV every 8 hours for 10 days
13. Prophylaxis: Varicella Immune Globulin (VZIG) Indications
    1. Immunodeficient under age 15 years
       1. Give within 72-96 hours exposure
    2. Newborn of infected mother
       1. Exposure 5 days before delivery or 2 days after
14. Prevention
    1. Avoid contact with active Shingles or Chicken Pox
    2. Consider prophylaxis if exposure in high-risk groups
    3. Varicella Vaccine routinely in children, teens, and adults
       1. May reduce risk of developing Shingles
       2. Part of routine Primary Series
    4. Herpes Zoster Vaccine (Shingles Vaccine, Zostavax)
       1. Recommended in adults over age 50 years (if not contraindicated)
       2. Following a Shingles episode, delay vaccination until acute Shingles has resolved prior to vaccination (~8 weeks)
       3. Reduces risk of Herpes Zoster Incidence by 60% and post-herpetic neuralgia by 65%
15. References
    1. Takhar in Majoewsky (2012) EM:Rap 12(11): 12
    2. Berger in Goldman (2000) Cecil Medicine, p. 2130-1
    3. Habif (1996) Dermatology, p. 351-9
    4. Gnann (2002) N Engl J Med 347:340-6
    5. Fashner (2011) m Fam Physician 83(12): 1432-7