By Gary M. White, MD
Herpes zoster (HZ) is an acute vesiculobullous eruption caused by reactivation of the varicella zoster virus (VZV). (Zoster means girdle and derives from the dermatomal distribution of the rash.) Varicella zoster virus causes both chickenpox and herpes zoster. After a bout of chickenpox, the VZV remains latent in nerve ganglion cells, typically sensory cells, for years. Reactivation occurs as the immune system surveillance wanes. The sexes are equally affected and the incidence increases with age--most acutely in those older than 60. 50% of people will develop HZ by 85 years of age. Children only rarely develop HZ.
The first evidence of this disease is typically pain felt by the patient. This pain is usually localized to the area that will subsequently develop the rash. Occasionally, the diagnosis can be quite difficult at this stage. If abdominal in location, such things as appendicitis, or gall bladder disease can be difficult to distinguish. One to three days after the onset of pain, the rash appears. The classic appearance of herpes zoster is grouped vesicles on an erythematous base scattered in a dermatome. One of the key diagnostic features is vesicles occurring up to, but not crossing over, the midline. Early on, the vesicles contain clear fluid, but within several days, the fluid becomes pustular and then crusting occurs. In mild cases, there are only individual groupings of vesicles. In severe cases, the entire dermatome is affected with confluent lesions. In some cases, the blisters become hemorrhagic. Ulceration or necrosis may rarely occur. If untreated, the skin lesions resolve in 2-4 weeks with younger patients tending to heal more quickly. Pain felt beyond one month from the onset of the rash is called postherpetic neuralgia (PHN). Various diseases have been noted to occur subsequently in the dermatome affected by herpes zoster. See disease following herpes zoster--dermatomal.
A few, scattered vesicular lesions may occur outside the dermatome (satellite lesions). If many are present, the term disseminated herpes zoster is used. The presence of satellite lesions convey a higher risk of severe disease. One study [BJD 2015;172;1530] found that the presence of satellite lesions conveyed a statistically significant relative risk for severe, multidermatomal and multistage HZ, systemic signs, immunosuppression (e.g., HIV, steroid use) and hospitalization.
HZ rarely presents in multiple dermatomes. When this occurs, a workup for immunodeficiency should be done.
Most children with HZ are immunocompromised, have a history of varicella, or were exposed to varicella in utero. However, HZ may occur in normal, healthy children due to either wild-type or vaccine-strain VZV. In a review of 22 cases of pediatric HZ in children who had previously received the VZ vaccine [Cutis 2017;90;207], the average age was 5.3 years. The average time between vaccination and HZ was 3.3 years. Of those tested, half had HZ caused by the vaccine strain and half wild type virus. The latter presumably had subclinical infection by the VZV prior.
If instituted early (e.g., within 72 hours of the onset of skin lesions), any of the medications listed above decreases pain, shortens healing time and decreases the risk of PHN. Such treatment is strongly recommended in those 50 years of age or over, with moderate or severe rash or pain, or in those with ophthalmologic involvement. In the immunocompromised, it should be given until healing occurs. One study showed famciclovir to be as effective as acyclovir 800 mg 5/day when given in any of 3 dosage schedules: 750 mg once a day, 500 mg BID, and 250 mg TID (all for 7 days).
The administration of systemic steroids (e.g., prednisone 60 mg initially and tapered over 2 weeks) is traditional, but controversial. If pain is severe, narcotic analgesics may be needed. The patient should be instructed that s/he can transmit chickenpox from the lesions until they scab over.
The herpes zoster vaccine (Zostavax) is a live, attenuated virus, FDA-approved for adults aged 50 and older. The vaccine is given once and the utility of revaccination is not clear. Studies indicate that the vaccine reduces the incidence of HZ and PHN 50-70% in the first 1-2 years with a waning effect after that and the effectiveness beyond 5 years uncertain. Thus, current recommendations by the Advisory Committee on Immunization Practices is for patients 60 and older to receive the HZ vaccine. Patients allergic to neomycin should not receive the vaccine as small amounts of the antibiotic are used in preparation of the vaccine. This live vaccine is also contraindicated in pregnancy and immunosuppressed states.
A study of the use of the HZ vaccine in older individuals with autoimmune diseases such as rheumatoid arthritis showed that the risk of HZ was reduced by an average of about 75% each year for 5 years, but the benefit waned after that [J Rheumatology 2017;Mar 15].
Recurrent herpes zoster (RHZ) is defined as a second or subsequent case of HZ in the same individual. In a review of 60 cases of RHZ [JAAD 2016;75;950], the annual incidence was 1%. Patients 50-79 years of age with RHZ had less severe skin lesions, less pain, and a lower risk of developing PHN compared with patients with primary HZ. These differences were not noted in those 80 years and older.
Herpes zoster in a child is often mild and may not require therapy. If indicated and if instituted within 72 hours of onset, adolescents may receive acyclovir 80 mg/kg/day in 4 or 5 divided doses not to exceed 4 gms/day. Younger children may be given oral acyclovir at a dose of 40-60 mg/kg/day.
The combination use of biologics with methotrexate for the treatment of psoriasis significantly increases the risk of herpes zoster (RR, 1.66). The use of acitretin lowers the risk (RR, 0.69) [JAAD 2015;151;533].
Note the prominent bases of erythema.
Courtesy Michael O. Murphy, MD
Herpes zoster in children.
Herpes zoster 14 days after starting a TNF agent for psoriasis.
Severe HZ with necrosis.
Solitary lesion of HZ on the glabella (culture-proven).
Chronic herpes zoster infection in AIDS patients.
Herpes Zoster Folliculitis. JAAD Case Reports January 2015 Volume 1, Issue 1, Pages 38–40
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