Diagnosis

Herpes zoster

Etiology

Cause

• Varicella-zoster virus (reactivation)

Patophysiology [3ug][y5q]

1. Varicella (chickenpox) is the initial self-limited varicella zoster virus infection

2. The virus remains dormant within dorsal root ganglia without causing any symptoms

3. Decades after the initial infection, the virus may reactivate and travel down nerve axons to cause herpes zoster (shingles)

   • Painful skin rash with blisters limited to the corresponding dermatome

4. Triggers for herpes zoster:

   • Emotional stress

   • Use of immunosuppressants

   • Acute or chronic illness

   • Exposure to the virus

   • Presence of a malignancy

5. Preeruptive stage (48 hours prior to rash): abnormal skin sensations or pain within the dermatome affected, headaches, general malaise, and photophobia

6. The acute eruptive phase (2-4 weeks): macules quickly transform into painful vesicles which rupture, ulcerate and eventually crust (most infectious and severe pain)

7. Chronic infection (>12 months): recurrent pain, paresthesias, shock-like sensations, and dysesthesias.

Risk factors

• Immunosuppression

• Cancer

• Age

Complications

• Postherpetic neuralgia

• Secondary bacterial infection

• Cranial neuropathies

• Shingles oticus (Ramsay Hunt syndrome type II): hearing loss and vertigo

• Polyneuritis

• Myelitis

• Meningitis

• Encephalitis

• Guillain-Barre syndrome

• Herpes Zoster Ophthalmicus/keratitis

Epidemiology

Incidence per 100.000 [gut][zsu][crz][5zm][qre]

Approach

• Blood test

• Tsanck smear

• PCR from blister

• Lumbar puncture

• Ophthalmoscopy

Treatment

Generally self-limited and resolve without intervention. Herpes zoster infection tend to be more benign and mild in children than in adults. Therapy might reduce the extent and duration of symptoms, and possibly the risk of chronic sequelae [3ug]:

1. Prevention: Varicella-zoster virus vaccine

2. Supportive care:

   • Wet dressing with 5% aluminum acetate (Burow solution) for 1 hour 5 times/day

   • Lotions (calamine)

3. Medications:

   • Analgesics/anti-inflammatory:

     • NSAIDs

     • Steroids

     • Topical lidocaine and capsaicin

     • Anticonvulsant agents (gabapentin)

   • Antiviral agents [y5q]

     • Topical acyclovir 5% cream

     • Systemic acyclovir and its derivatives (valacyclovir and famciclovir)

       • Acyclovir 800 mg five times daily for 5 days

       • Valacyclovir 1 gram three times daily for 5 days

4. Admission to hospital if:

   • Severe symptoms

   • Immunosuppression

   • Atypical presentations (eg, myelitis)

   • Involvement of more than 2 dermatomes

   • Significant facial bacterial superinfection

   • Disseminated herpes zoster

   • Ophthalmic involvement

   • Meningoencephalopathic involvement

Differential diagnoses

Acneiform eruptions, Acne keloidalis nuchae, Acute poliomyelitis, Angina pectoris, Aphthous stomatitis, Appendicitis, Bell's Palsy, Brain tumor, Candidiasis, Cellulitis, Chickenpox, Cholecystitis, Cholelithiasis, Conjunctivitis, Contact dermatitis, Cowpox infection, Coxsackievirus infection, Dental infection, Ecthyma, Eczema, Encephalitis, Erysipelas, Erysipeloid, Folliculitis, Furunculosis, Glaucoma, Herpangina, Herpes simplex, Insect Bite, Iridocyclitis, Jellyfish stings, Keratitis, Lichen striatus, Lyme disease, Lymphangioma circumscriptum, Measles, Meniere disease, Meningitis, Multiple sclerosis, Myasthenia gravis, Optic neuritis, Retinitis, Spinal disc herniation, Spinal stenosis, Stroke, Superficial pyoderma, Syphilis, Trigeminal neuralgia, Urinary tract infection, Urolithiasis, Uveitis, Vestibular neuronitis