- Viral exanthems are usually asymptomatic and self-limited and therapy usually is not required.
- Recognition of the viral etiology is mostly indicated for counseling patients regarding the course of the infection and regarding appropriate isolation precautions. It is very important to make the correct specific viral diagnosis during pregnancy (laboratory testing should be undertaken), as rubella and varicella can cause severe congenital abnormalities.
- Vaccination of infants and children for viral infections is an important and effective step towards prevention and spread.
- Antiviral therapies, such as antiviral medications or intravenous immunoglobulin, may be indicated for severe viral infections in immunocompromised patients.
Skin rashes are seen in a variety of viral illnesses and may be the presenting sign of disease to a primary care physician. While many of these viral illnesses are typically seen in childhood, a number of them occur in adulthood and should be considered in the setting of travel to endemic regions, particularly in patients with incomplete or waning immunity (and especially in those who have not been vaccinated).
Many viral exanthems are accompanied by an enanthem (oral mucosal lesions) which may in some cases provide clues to the etiology.
While the majority of viral exanthems are self-limited and minimally symptomatic to asymptomatic, treatment is occasionally warranted, either for the symptoms of the skin rash (most commonly pruritus) or for other organ involvement by the virus. For an overview of characteristic features, diagnosis and management of the classic viral exanthems, see table, Viral Exanthems: Features, Diagnosis & Management.
Patients with a viral exanthem often present with a non-specific morbilliform eruption. In some cases, the skin disease as part of a constellation of other symptoms may indicate a specific viral etiology. All patients presenting with a suspected viral exanthem should be evaluated with a thorough history (including onset of symptoms and exposures and affected contacts) and review of systems. A physical exam should include the oral mucosa, as some viruses have a characteristic enanthem. If presentation is severe or the patient is in a high-risk group (especially pregnant or immune compromised), diagnostic testing should be undertaken.
Parvovirus B19, a.k.a. erythema infectiosum
Exanthem subitum (roseola infantum)
Coxsackie virus (Hand-foot-mouth disease)
The differential diagnosis of viral exanthem includes morbilliform drug eruption, graft versus host disease, Kawasaki disease, and a variety of other non-viral infectious rashes including secondary syphilis, Rocky Mountain spotted fever, and scarlet fever caused most commonly by group A streptococcus. A careful drug history is indicated in the evaluation of a patient with a possible viral exanthem.
Morbilliform drug eruption
Secondary syphilis, caused by the spirochete bacterium Treponema pallidum, results in a generalized eruption with scaly erythematous papules, characteristically with palmo-plantar involvement. Additional signs, such as mucous patches, condyloma lata, and patchy alopecia accompany the cutaneous eruption in the second phase of syphilis.
First-line therapy: Therapy is usually not required; most treatments are directed towards skin symptoms only. Exceptions include severe disease/immunocompromised patients or pregnant women with varicella, in which case antiviral treatment with acyclovir (or other drugs in this class) and/or varicella immune globulin may be appropriate.
Skin-directed therapy for patients with vesiculobullous lesions and/or pruritus:
- Antihistamines (e.g., hydroxyzine 10-25 mg t.i.d. [such as Atarax], diphenhydramine 25-50 mg t.i.d. [such as Benadryl], or chlorpheniramine 4-16 mg/day) can be used to alleviate pruritus.
- For pediatric cases,hydroxyzine syrup (dosed at 1-2 mg/kg/day divided 3-4 times daily) or diphenhydramine elixir (6.25 mg for ages 2-5, 12.5-25 mg for ages 6-11, 25-50 mg for ages 12 and older) every 6 to 8 hours or at bedtime can be used.
- Tepid baths with added colloidal oatmeal (such as Aveeno) are useful for both relief of pruritus and debridement of vesiculobullous lesions.
- A topical emollient or antipruritic lotion containing menthol, camphor, and/or pramoxine (such as Sarna, Prax) can provide symptomatic relief. Note: These agents should be used cautiously as they may induce an allergic response or irritation of the skin.
- Consider a drug eruption in the differential diagnosis in patients with a medication exposure history.
- Antihistamines can cause drowsiness or a paradoxical hyperactivity, particularly during the first few days of therapy.
- Arthritis and meningitis are rare complications of viral illnesses, although they occur with greater frequency in affected adults than children.
- Viral exanthems can induce an aplastic crisis in patients with hematologic disease (sickle cell anemia, G6PD deficiency) and in immunocompromised individuals.
- 30-year-old healthy woman with several weeks of somewhat pruritic papular rash on the trunk that was preceded by a larger scalier oval plaque
- No sick contacts
- Clinical presentation is typical for pityriasis rosea
- Recommend topical emollients and other gentle skin care; can consider topical corticosteroids if significant pruritus
- Follow-up as needed; most cases resolve within 2-8 weeks
- 42-year-old man recently immigrated from Southeast Asia with fever, upper respiratory infectious symptoms, and mildly pruritic papulovesicular rash that started on his trunk and is generalizing over the past few days, now with extensive facial involvement
- Patient reports he did not receive childhood vaccinations and was recently exposed to an elderly person with shingles
- Patient is immunocompetent
- Clinical presentation with lesions at various stages of development is typical for primary varicella infection (versus disseminated zoster—the distinction would be made based on patient’s lack of history of primary varicella infection in childhood and could theoretically be confirmed by a negative VZV IgG). Confirmatory testing could include direct fluorescent antibody (DFA) or VZV PCR from vesicle fluid, or histopathology
- Given the elevated risk of complications (particularly VZV pneumonitis), recommend close monitoring and consider hospital admission
- Patient should receive acyclovir 800 mg po 5x daily x 5-7 days, ideally started within 24 hours of rash onset
- Low threshold for lumbar puncture if the patient develops CNS symptoms—CNS involvement of VZV would necessitate IV acyclovir
- Recommend colloidal oatmeal baths daily with topical emollients and mentholated emollients as needed
- Recommend hydroxyzine 25-50 mg at bedtime for nocturnal pruritus
- Given high risk of transmission, patient should be isolated from others until lesions are crusted over (airborne and contact precautions if he is hospitalized)
- Follow-up as needed
Folster-Holst R, HW Kreth. (2009) Viral exanthems in childhood: Part 1, 2, and 3. Journal of the German Society of Dermatology, 7:309-316 (Part 1), 7:414-418 (Part 2), and 7:506-510 (Part 3).
Leonid I, Evelyn L. (2009) Primary varicella in an immunocompetent adult. J Clin Aesthet Dermatol, Aug;2(8):36-8.
Nelson JS, Stone MS. (2000) Update on selected viral exanthems. Curr Opin Pediatr, Aug;12(4):359-64.
Scott LA and MS Stone. (2003) Viral Exanthems, Dermatology Online Journal, 9(3):4.