Viral exanthems

Published on 11/06/2015 by admin

Filed under Pediatrics

Last modified 22/04/2025

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Koplik’s spots. Red buccal mucosa with 1-mm white macules in a child with measles.

Infectious mononucleosis. Widespread red papules over chest of pre-teen.

Erythema infectiosum. Lacy rash on both extremities and trunk following red cheeks.

Aymmetric periflexural exanthem with lacy rash on one inner arm.

CLINICAL FEATURES

Viral exanthems are quite common in childhood. Two major patterns are discrete red papules and macules (measles-like or morbilliform) and a lacy red macular pattern.

Morbilliform eruptions are seen in rubeola, rubella, roseola, enterovirus infections and infectious mononucleosis. The child with roseola (measles) has a prodrome of high fever, barking cough, rhinitis and conjunctivitis lasting 3 to 5 days, followed by red oral mucosa with 1−2-mm white macules (Koplik’s spots). A generalized morbilliform eruption follows accompanied by cervical lymphadenopathy. Bacterial otitis media, pneumonia or encephalitis may complicate.

Rubella is a mild illness with a 3-day morbilliform rash and mild lymphadenopathy. Monoarticular arthritis can occur. Pregnant women exposed to rubella during the first trimester are at risk for congenital rubella, with heart, ear, eye and CNS defects.

Roseola (HHV 6 infection) presents in toddlers with high fever yet appearing well. Rarely, convulsions at the onset of fever are described. After 2 or 3 days of fever a transient morbilliform rash occurs.

Infectious mononucleosis (HHV 4, 5, 6 & 7 infections) is characterized by fever, generalized lymphadenopathy, fatigue, sore throat with exudative tonsillitis, headache and splenomegaly. The morbilliform eruption lasts 1 to 5 days; fatigue can last up to 3 months. Serology for EBV IgM is positive and the most reliable diagnostic test. Liver function tests are often abnormal. In some, arthritis can occur and persist several months. Drug eruptions mimic exanthems.

Lacy-like eruptions are seen in erythema infectiosum (parvovirus B19 infection) and the asymmetric periflexural exanthem.

Erythema infectiosum has a distinct pattern of confluent red cheeks and a lacy red pattern on extremities and trunk that lasts 3 to 5 days but will recur upon sun exposure or overheating of the skin. A transient arthritis may develop.

Parvovirus B19 replicates within red blood cells and causes disruption of red cell production. In children with chronic hemolytic anemias, an aplastic crisis can occur. Pregnant women exposed to parvovirus B19 can have a fetus with hyrdops fetalis.

Asymmetric periflexural exanthema shows a lacy eruption on one side of the body lasting 1 to 3 days in an otherwise well child.

TREATMENT

Supplements of vitamin A in measles have reduced pulmonary disease. Measles immune globulin administered within 6 days may modify the disease.

Roseola and rubella usually require no treatment.

Infectious mononucleosis splenomegaly may be improved with systemic steroids reducing the risk of splenic rupture.

Erythema infectiosum and the asymmetric exanthema require no intervention. In suspected rubella or erythema infectiosum, avoidance of pregnant women is advised.