Family physicians encounter skin rashes on a daily basis. First steps in making the diagnosis include identifying the characteristics of the rash and determining whether the eruption is accompanied by fever or any other symptoms. In the article that follows, we review 8 viral exanthems of childhood that range from the common (chickenpox) to the not-so-common (Gianotti-Crosti syndrome).
Varicella-zoster virus (VZV) is a human neurotropic alphaherpesvirus that causes a primary infection commonly known as chickenpox (varicella).1 This disease is usually mild and resolves spontaneously.
This highly contagious virus is transmitted by directly touching the blisters, saliva, or mucus of an infected person. It is also transmitted through the air by coughing and sneezing. VZV initiates primary infection by inoculating the respiratory mucosa. It then establishes a lifelong presence in the sensory ganglionic neurons and, thus, can reactivate later in life causing herpes zoster (shingles), which can affect cranial, thoracic, and lumbosacral dermatomes. Acute or chronic neurologic disorders, including cranial nerve palsies, zoster paresis, vasculopathy, meningoencephalitis, and multiple ocular disorders, have been reported after VZV reactivation resulting in herpes-zoster.1
Presentation. With varicella, an extremely pruritic rash follows a brief prodromal stage consisting of a low-grade fever, upper respiratory tract symptoms, tiredness, and fatigue. This exanthem develops rapidly, often beginning on the chest, trunk, or scalp and then spreading to the arms and legs (centrifugally) (FIGURE 1). Varicella also affects mucosal areas of the body, such as the conjunctiva, mouth, rectum, and vagina.
The lesions are papules that rapidly become vesicular with clear fluid inside. Subsequently, the lesions begin to crust. Scabbing occurs within 10 to 14 days. A sure sign of chickenpox is the presence of papules, vesicles, and crusting lesions in close proximity.
Complications. The most common complications of chickenpox—especially in children—are invasive streptococcal and staphylococcal infections.2 The most serious complication occurs when the virus invades the spinal cord, causing myelitis or affecting the cerebral arteries, leading to vasculopathy. Diagnosis of VZV in the central nervous system is based on isolation of the virus in cerebral spinal fluid by polymerase chain reaction (PCR). Early diagnosis is important to minimize morbidity and mortality.
Reactivation is sometimes associated with post-herpetic neuralgia (PHN), a severe neuropathic pain syndrome isolated to the dermatomes affected by VZV. PHN can cause pain and suffering for years after shingles resolves, and sometimes is refractory to treatment. PHN may reflect a chronic varicella virus ganglionitis.
A number of treatment choices exist for shingles, but not so much for varicella
Oral treatment. Oral medications such as acyclovir and its prodrug valacyclovir are the current gold standards for the treatment of VZV.3
Famciclovir, the prodrug of penciclovir, is more effective than valacyclovir at resolving acute herpes zoster rash and shortening the duration of PHN.4 Gabapentinoids (eg, pregabalin) are the only oral medications approved by the US Food and Drug Administration (FDA) to treat PHN.5
Topical medications can also be used. Lidocaine 5% is favored as first-line therapy for the amelioration of pain due to shingles, as it provides modest pain relief with a better safety and tolerability profile than capsaicin 8% patch, which is a second-line choice. The latter must be applied multiple times daily, has minimal analgesic efficacy, and frequently causes initial pain upon application.
Gabapentinoids and topical analgesics can be used in combination due to the low propensity for drug interactions.6,7 The treatment of choice for focal vasculopathy is intravenous acyclovir, usually for 14 days, although immunocompromised patients should be treated for a longer period of time. Also consider 5 days of steroid therapy for patients with VZV vasculopathy.8
Non-FDA approved treatments include tricyclic antidepressants (TCA), such as amitriptyline, nortriptyline, and desipramine, which are sometimes used as first-line therapy for shingles. TCAs may not work well in patients with burning pain, and can have significant adverse effects, including possible cardiotoxicity.9
Opioids, including oxycodone, morphine, methadone, and tramadol, are sometimes used in pain management, but concern exists for abuse. Because patients may develop physical dependence, use opioids with considerable caution.10
Prevention. The United States became the first country to institute a routine varicella immunization program after a varicella vaccine (Varivax) was licensed in 1995.11 The vaccine has reduced the number of varicella infection cases dramatically.11 Vaccine effectiveness is high, and protective herd immunity is obtained after 2 doses.11-13 The vaccine is administered to children after one year of age with a booster dose administered after the fourth birthday.
A live, attenuated VZV vaccine (Zostavax) is given to individuals ≥60 years of age to prevent or attenuate herpes zoster infection. This vaccine is used to boost VZV-specific cell-mediated immunity in adults, thereby decreasing the burden of herpes zoster and the pain associated with PHN.14