Herpes Zoster: Practice Essentials

Herpes zoster (shingles) is an acute viral illness that causes a characteristic painful vesicular rash in a dermatome pattern. It is caused by reactivation of varicella-zoster virus (VZV), a double-stranded DNA herpes virus, that has remained dormant within dorsal root ganglia in a person’s body following primary infection with varicella (chicken pox) in early life. Though the mechanism is not clearly understood there are certain risk factors which cause the reactivation of dormant virus and include increased age, poor immune system, stress, disease states, chickenpox before age of 18 months, radiation and certain medication.

Herpes zoster is contagious and transmitted via direct contact with active lesions or respiratory droplets. The symptoms started with pain or abnormal skin sensation in the affected dermatome which indicated the onset of rash by 2-3 days. The patient also experiences flu-like symptoms, headache, malaise, myalgia or fever. This phase is known as preerruptive phase (preherpetic neuralgia). This phase is then followed by an acute eruptive phase where there is an appearance of erythematous macules and papules which rapidly developed into vesicles and bullae over a period of 3-5 days (classic finding of herpes zoster rash).

The lesions then passes through various phases of wear and tear, rupture and release of content of vesicles, ulceration and formation of crust. Herpes Zoster has an excellent prognosis and the symptoms get resolve over 10-15 days with complete healing of lesions usually in a month. Some patients, however, develop persistent or recurrent nerve pain in the area after the resolution of rash which last weeks, months, or years. This is known as Postherpetic neuralgia (PHN) and is the most frequent complication of herpes zoster which causes significant economic burden.

PHN is the chronic phase which is seen more frequently when upper body dermatome is involved or after cases of herpes zoster ophthalmicus (HZO). Other complications of herpes zoster are herpes zoster ophthalmicus, myelitis, cranial neuropathies, secondary bacterial infection, Ramsay Hunt syndrome, aseptic meningitis, encephalitis, pneumonitis or hepatitis. Mortality is rare but seen in elderly and immunocompromised patients with disseminated zoster due to these complications. Herpes zoster has no sex predilection and seasonal or epidemic preponderance.

Its incidence rate is similar worldwide. The lifetime incidence rate of herpes zoster in general population is 10-20%. The incidence increases with age with rises to 50% surviving to 85 years of age. The next day I received a call from a dermatologist who consulted the patient and it developed a maculopapular rash with an erythematous base with classic herpetiform vesicles in a dermatome pattern on right flank region that confirms the diagnosis of herpes zoster and hence no further testing or treatment was required.

Learning points It is a good reminder and I always encourage myself and colleagues to never underestimate the power of visual inspection of the disease or affected part of the body. Trust me or not this is often missed in ER or urgent care settings due to increasing turnover and heavy loads of the patients unless someone ended up with rashes, allergies or burn complaint. With visual inspection, one can change his approach to diagnose, test and treat the patient.

Though the patient’s initial presentation and his past history suggestive of renal calculi but visual inspection of the affected area and discrepancy of pain with his labs and imaging guide to diagnosis and a new management plan. Discussion: Herpes zoster is a clinical diagnosis based on history and physical examination. With characteristic skin lesion, no further testing is required. However, in atypical cases especially in immunocompromised patients or where the diagnosis is uncertain between herpes zoster and other herpes viruses infections we can use following laboratory studies:

1. Tzanck smear of vesicular fluid (lower sensitivity and specificity than DFA or PCR)

2. Direct fluorescent antibody (DFA) testing of vesicular fluid or a corneal lesion

3. Polymerase chain reaction (PCR) testing of vesicular fluid, a corneal lesion, or blood Tzanck smear is the least expensive and simplest laboratory method that confirms the lesions of herpetic but it cannot differentiate between herpes zoster and other herpesviruses.

DFA and PCR testing are used for acute confirmation that allows differentiation between VZV and other herpes viruses infections by detecting VZV antigen. Most of these tests are time-consuming, lack specificity and unavailable. Herpes Zoster is usually a self-limited disease and management revolve around pain control and care of the wound. Medications used in acute pain are nonsteroidal anti-inflammatory drugs (NSAIDs), narcotic and nonnarcotic analgesics (topical or systemic), neuroactive agents (eg, tricyclic antidepressants), and anticonvulsant agents (eg, gabapentin, pregabalin).

Calamine lotion or capsaicin cream or wet dressings with 5% aluminum acetate are applied for 30-60 minutes four times daily. Oral antiviral medications (acyclovir 800mg five times daily, famciclovir 500mg three times daily and valacyclovir 1g three times daily) are more effective when used within 72 hours of the onset of symptoms or appearance of the rash and continue for five days. They are not only shortening the duration of disease course but also prevent and decrease the severity of postherpetic neuralgia.

The use of steroid is still controversial. Some physicians still recommend 40-60mg oral prednisone with the start of the disease is continued for 1 week followed by a rapid taper over a period of 1-2 weeks. In some cases, hospital admission is required where more than two dermatomes are involved, ophthalmic involvement, postherpetic neuralgia or in immunocompromised patients. In the United States, the Centers for Disease Control and Prevention recommend shingle vaccine for adults age 60 years and older to prevent shingles.

It is very cost effective and also reduces the risk of the duration of symptoms and developing post-herpetic neuralgia. Conclusion to see your patients getting the right treatment at the right time and when they come back with positive feedback. Also, I learned sometimes you just do not assume if someone has a personal or past history of some disease then he or she might end up with a flare-up of same symptoms again we have to think out of the box.