Viral exanthems: rubella, roseola, rubeola, enteroviruses



Viral exanthems


rubella, roseola, rubeola, enteroviruses


Michael Romano, Jeffrey Mailhot and Karen Wiss


Evidence Levels:  A Double-blind study  B Clinical trial ≥ 20 subjects  C Clinical trial < 20 subjects  D Series ≥ 5 subjects  E Anecdotal case reports


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Rubella


Rubella (German measles, 3-day measles) is usually a mild disease of low-grade fever, generalized erythematous macules and papules, and generalized lymphadenopathy. It is caused by an enveloped RNA virus of the Togaviridae family.



Management Strategy


In children, there is typically no prodrome. In adolescents and adults, a prodrome of fever, malaise, sore throat, nausea, anorexia, and generalized lymphadenopathy is often seen. The erythematous pink macules and papules start on the face and neck and spread down and out in a centrifugal fashion over 1–2 days. These lesions disappear in 2–3 days. Forschheimer spots, an enanthem consisting of petechiae on the hard palate, may accompany the rash.


Rubella is a self-limited illness. The treatment is generally supportive. Teenagers and adults may experience transient polyarthralgia and polyarthritis. Thrombocytopenia and encephalitis are extremely rare complications. During the first trimester of pregnancy, maternal rubella can result in fetal death or congenital rubella syndrome. The main fetal anomalies include ophthalmic disease (cataracts, glaucoma, microphthalmia, and chorioretinitis), sensorineural deafness, cardiac abnormalities (patent ductus arteriosus, atrial septal defects, ventricular septal defects), pulmonic stenosis, and blueberry muffin lesions (extramedullary hematopoiesis).


It can be difficult to distinguish rubella from other viral exanthems, in particular enteroviruses. Rubella also mimics measles, parvovirus B19, human herpesvirus (HHV)-6, and arboviruses. It is essential to differentiate infection between these viruses during pregnancy. Virus identification by culture is available. In congenital infections, rubella can be isolated from the blood, urine, cerebrospinal fluid, and the posterior pharynx. In postnatal infections, the virus is harbored in the nasopharynx. Amplification is accomplished by reverse transcription polymerase chain reaction (RT-PCR). Viral serology is also available for diagnosis. Both serum IgM and seroconversion of convalescent IgG with a fourfold increase in titer suggest recent infection. A more reliable diagnosis is obtained by both RT-PCR and serology, which can detect virus on day 0 of rash eruption. Microarray technology is a cheap and promising future methodology for diagnosis of acute infection. Children with rubella should be excluded from school for 7 days after onset of the rash. Rubella vaccine is recommended in combination with the measles and mumps vaccine, with or without the varicella vaccine (MMR or MMRV), at 12–15 months of age with a second dose at 4–6 years. However, an increased risk of febrile seizures has been reported with the combination MMRV vaccine. Post-pubertal females can be tested for rubella IgG and vaccinated if necessary. The vaccine contains live virus and should not be given to pregnant women.



Specific investigations












First-line therapies


















image Antipyretics: acetaminophen (paracetamol), ibuprofen E
image Analgesics: non-steroidal anti-inflammatory drugs E
image School avoidance for 7 days A
image Immunization A




Roseola


Roseola infantum (exanthem subitum, sixth disease) is a disease of high fever in a well-appearing child with an exanthem of pink macules and papules upon defervescence. It is caused by infection with HHV-6 or -7.



Management Strategy


Roseola is an illness of children between 6 and 36 months of age. The first sign of illness is a high fever (>39.5°C) that persists for 3 to 7 days, followed by an exanthem that spreads centrifugally from the neck, lasting hours to days. Typically, no treatment is necessary and the illness resolves in a few days. Febrile seizures are common in infants during the febrile phase, usually requiring emergency room care.


Identification of HHV-6 or -7 is difficult because most infections are asymptomatic. Culture from peripheral blood is available in specialized facilities but is of limited use due to slow turn-over. High population seroprevalence (~95%) also renders serology less useful. Seroconversion of convalescent IgG with a fourfold increase in titer is more indicative of acute infection. However, there is considerable antibody cross-reactivity between HHV-6, -7, and cytomegalovirus (CMV). Viral DNA detection by nucleic acid amplification of whole blood, serum, or plasma is the current method of diagnosis, though standardized methods of measurement are yet to be determined. Recent studies suggest that PCR alone cannot reliably distinguish between active and latent infection; a multiple assay approach is more sensitive and specific.


Most individuals harbor HHV-6 and -7 in their saliva, while only 1% of the population carries chromosomally integrated viral DNA. In the immunocompromised, viral reactivation frequently causes severe disease such as fever, bone marrow suppression, hepatitis, pneumonia, lymphoproliferative disorders, and encephalitis. In these patients, ganciclovir and foscarnet are first-line treatments. Foscarnet has shown prophylactic efficacy in stem-cell transplant patients. In vitro studies show that ganciclovir, cidofovir, and foscarnet inhibit HHV-6 and -7 replication. Individual case reports have suggested benefit from these agents in immunocompetent patients with end-organ disease. Infection with HHV-6 can be associated with a severe course of drug-induced hypersensitivity syndrome.

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Aug 7, 2016 | Posted by in Dermatology | Comments Off on Viral exanthems: rubella, roseola, rubeola, enteroviruses

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