creation date: 2026-04-05 19:31
tags: Pathologies
Herpes Zoster
Background
Definitions
Herpes zoster, also known as shingles, refers to disease due to the reactivation of latent varicella-zoster virus (VZV). This is characterized by a distinct rash, pain, and potentially numerous complications.
Etiology and Pathogenesis
Herpes zosters originates from latent VZV. The initial primary infection by VZV is varicella, or chickenpox. During the initial infection, VZV infects nasopharyngeal lymphoid tissue which results in VZV-infected T cells that can travel through the body.
Following a prolonged incubation period, the varicella rash develops and virus present in the skin vesicles infect the nerve endings in the skin. The virus move retrograde along sensory axons and establish life-long latency in neurons within the regional ganglia.
In a healthy individual, immune responses developed during varicella course controls VZV latency and limits the opportunity for reactivation. However, should host immune response weakens, VZV reactivation occurs and spread antegrade down the sensory nerve resulting in the classic rash. Reactivation is not limited to a single neuron and can spread within the ganglion.
As VZV replication continues, the involved ganglion becomes intensely inflamed and nerve cells undergo hemorrhagic necrosis. Neuronal damage results in neuropathic pain.
Active herpes zoster lesions can transmit VZV, causing varicella, by aerosolized particles.
Risk Factors
Herpes zoster can only occur if the host has had varicella. It should be noted that unless vaccinated, there is a possibility of prior sub-clinical infection that can result in herpes zoster despite a negative history.
Risk factors for reactivation include:
- Age (>50, increases with age)
- Immunocompromised status (eg. transplant, autoimmune, HIV)
- Female sex
- Physical trauma
- Comorbidities (malignancy, immune disorders, chronic lung or kidney disease)
Clinical Presentation
Signs & Symptoms
Uncomplicated herpes zoster present with rash and acute neuritis.
The rash follows a single dermatome or several contiguous dermatome. Typical course is:
- Erythematous papules
- Grouped vesicles or bullae
- Pustular that can be hemorrhagic if immunosuppressed or advanced age
- Scarring and pigmentation changes (may persist for months to years)
Acute neuritis presents with pain that is described as “burning”, “throbbing”, or “stabbing”. This pain may precede the rash, typically by 2-3 days.
In rare cases of uncomplicated disease, systemic symptoms may be present.
- Headache
- Fever
- Malaise
- Fatigue
Following the disease course, a common complication is postherpetic neuralgia. This is significant pain persisting for 90 days after onset of rash. Other sensory symptoms include:
- Numbness
- Dysesthesia
- Pruritus
- Allodynia
Complicated disease consist of herpes zoster with ocular, otic, or neurologic disease:
Herpes zoster opthalmicus
- Involvement of the ophthalmic division of the trigeminal nerve (CN5, V1)
- Prodrome of headache, malaise, fever
- Unilateral pain or hypesthesia in affected eye, forehead, and top of head
- Hyperemic conjunctivitis, uveitis, episcleritis, and keratitis occurring with onset of rash
- Corneal involvement can result in vision loss
Acute retinal necrosis
- Acute iridocyclitis, necrotizing retinitis, occlusive retinal vasculitis
- Rapid loss of vision
- Eventual retinal detachment
Herpes zoster oticus (Ramsay Hunt syndrome)
- Ipsilateral facial paralysis, ear pain, and vesicles in auditory anal or on auricle
- Ipsilateral taste alterations, hearing abnormalities, lacrimation, vertigo occasionally
Central neurologic complications
- Aseptic meningitis
- Encephalitis
- Peripheral motor neuropathy
In immunocompromised hosts, herpes zosters may occur recurrently and present as disseminated infection.
History & Physical Exam
History should include:
- Prodromal symptoms
- Past history of varicella infection (note that subclinical infection may have occurred without the patient knowing)
- Vaccination status for varicella
Physical exam of the rash for dermatomal distribution.
Diagnosis
Criteria
Diagnosis is usually made clinically based on the presence of a painful vesicular eruption with a well-defined dematomal distribution.
Diagnostic testing can be used for uncertain diagnoses:
- PCR testing (preferred)
- Direct fluorescent antibody (DFA) testing
- Viral culture
Work-up
If symptoms and signs involve the eye, an ophthalmologist should be consulted.
Differential
Alternative diagnoses include other rashes, particularly herpes simplex lesions.
Red Flags / Complications
Major complications are:
- Vision loss
- Mortality due to disseminated disease (particularly visceral dissemination following stem cell or organ transplant)
- Bacterial superinfection of the soft tissue
Management
Prevention
Vaccinations are available for both varicella and herpes zoster.
The varicella vaccine is routinely given at 15 months.
The herpes zoster vaccine is recommended for patients ≥50 years of age without contraindication. Patients ≥50 who had a previous episode should be vaccinated after at least one year. OHIP covers the vaccination for adults ≥65 years old.
- 2-doses IM, with second dose administered 2-6 months after first dose
Treatment of Herpes Zoster
Antiviral therapy
Antivirals are used to prevent formation of new lesions and speed up recovery. They are indicated if:
- Patient presented within 72 hours of clinical manifestations
- Patients presented after 72 hours but is immunocompromised or there is risk of complications (eg. potential ocular involvement)
Regimen options include:
- Valacyclovir 1000 mg TID
- Famciclovir 500 mg TID
- Acyclovir 800 mg 5x/day (preferred in pregnancy due to more experience)
Pain management
While antiviral therapy reduces acute neuritis-associated pain, moderate to severe pain may still require additional analgesia.
Generally, mild to moderate pain can be managed with:
- Acetaminophen
- NSAIDs
For severe pain, choices depend on comorbidities, concurrent medications, intensity, and preferences:
- Short-acting opioids (eg. oxycodone)
- Corticosteroids
- Gabapentin
Complicated disease
Depending on manifestation of complications, patients may require IV, prolonged, or adjunctive therapy.