Chickenpox in an elderly man

Discussion

PubMed and MEDLINE searches were completed using the 2 MeSH terms chickenpox and varicella zoster virus infection, with preference given to review articles published after 1995. Article references were hand searched for relevant publications.

The incidence of PV in Canada has declined substantially with implementation of routine varicella vaccination programs in the pediatric population across provinces and territories between 2000 and 2007.² Annual incidence of PV has declined from 214.3 cases per 100 000 before the vaccine to 3.1 cases per 100 000 between 2011 and 2015.² Children benefit from protection rates of 94.4% and 98.3% following a single dose and a second dose of varicella vaccine, respectively.⁵ This decline in PV incidence has resulted in decreased suspicion and detection rates among clinicians.⁶

Varicella-zoster virus is highly contagious and is transmitted through airborne droplets or direct contact with vesicular fluid.⁴ Transmission of VZV can occur from either PV or HZ. The affected individual is infectious beginning from 2 days before the onset of rash and remains infectious until all vesicles have crusted (typically 5 days after rash onset).⁴ The incubation period of VZV is 10 to 21 days.⁷

A family physician’s office is often the first place that patients will visit when ill, hence it is important that family physicians recognize PV early on to prevent transmission to other patients. Nosocomial transmission of VZV is primarily airborne.⁸ Early recognition is not only crucial to prevent transmission but also to prevent potentially life-threatening effects on others, such as pregnant women and their fetuses. Mortality rates from PV are higher in pregnant women than nonpregnant women, and potential maternal complications include respiratory pneumonitis.⁹ Fetal complications can include birth malformations from congenital varicella syndrome or multiorgan failure in neonates, especially if PV infection occurs during gestational weeks 13 to 20.⁵

Primary varicella presents with discrete pruritic papules and vesicles in different evolutionary stages, with the classic description “dewdrop on a rose petal.”¹⁰ The rash typically starts on the head and neck before spreading to the trunk and extremities in a cephalocaudal progression. Younger clinicians might be unfamiliar with the presentation of PV, as its incidence has declined.^6,11 Primary varicella is usually seen in susceptible unvaccinated individuals, but can also present in individuals who had been previously vaccinated, which is referred to as “breakthrough varicella.”¹² In otherwise healthy children, PV is relatively benign, mainly limited to cutaneous involvement.⁴ However, infection from PV in healthy adults can result in more severe disease and higher rates of complications.⁴ In high-risk populations, such as immunodeficient or pregnant individuals, PV can disseminate and involve multiple organ systems.⁴ Disseminated PV is associated with high morbidity and mortality, with complications including myocarditis, gangrene, hepatitis, and glomerulonephritis.¹³ Hepatitis and glomerulonephritis likely occurred in this patient.

The differential diagnosis in this patient includes disseminated HSV or disseminated HZ. Disseminated HSV typically presents with painful, grouped vesicles on a confluent erythematous base. Primary varicella and disseminated HSV histopathology findings from a skin biopsy can look identical, hence viral polymerase chain reaction of vesicular fluid is necessary to differentiate the 2 viruses.¹⁴ Herpes zoster typically presents with grouped vesicles in a unilateral, dermatomal distribution. Disseminated HZ can involve multiple dermatomes and can be bilateral. However, dermatomal involvement remains visible and will aid diagnosis. While hepatic dysfunction alone can occur in adults with PV, the concomitant presentation of acute-on-chronic kidney disease, fluctuating level of consciousness, and hepatic dysfunction in the patient presented in this case suggests disseminated PV. A lumbar puncture and cerebral magnetic resonance imaging were contraindicated owing to the patient’s pacemaker and overlying rash on the spine.

For susceptible individuals who are healthy, nonpregnant, and older than 12 months of age, the varicella vaccine can be administered up to 5 days after exposure to prevent or reduce the severity of PV.⁵ For nonimmune individuals who are ineligible to receive the varicella vaccine, such as infants, pregnant women, or immunocompromised individuals, an alternative post-exposure treatment is varicella zoster immune globulin.⁵ If varicella zoster immune globulin is unsuccessful at preventing PV, it might still reduce the disease severity if given within 10 days after exposure.⁵ Varicella zoster immune globulin is most efficacious if given within 4 days after exposure.⁵

Acyclovir is the first-line treatment option for PV to prevent disease progression, prevent complications, and hasten recovery. Acyclovir is typically used in the high-risk populations described,¹⁵ but acyclovir use in immunocompetent children has been shown to result in a shorter duration of disease, fewer skin lesions, and accelerated lesion healing.¹⁶ Acyclovir should be considered in all individuals regardless of immune status or disease severity.¹⁷