Erythema infectiosum is a viral infection caused by parvovirus B19, presenting most commonly between 4 and 10 years of age. It begins with nonspecific prodromal symptoms including malaise, coryza, headache, fever, nausea, and diarrhea. In 25% of cases, the classic rash appears 2 to 5 days into the illness and is characterized initially by the “slapped cheeks” appearance of a bright red malar, macular rash that spares the nasal ridge and perioral areas. A reticulated, lacy erythematous maculopapular eruption with central clearing then appears on the extensor surfaces of extremities. The differential diagnosis includes other morbilliform eruptions such as measles, rubella, roseola, and infectious mononucleosis. Bacterial infections (eg, scarlet fever), drug reactions, and other skin conditions such as guttate psoriasis, papular urticaria, atopic dermatitis, and erythema multiforme are also included in the differential.
Management and Disposition
Treatment is aimed at symptomatic relief. Parents can be reassured that this exanthem is benign and self-limited. Once the rash appears, the patient is no longer contagious. It is important to educate the patient and family about the possible risk of parvovirus B19 as a cause of hydrops fetalis or fetal deaths early in pregnancy. It can also cause a transient and, rarely, permanent aplastic crisis in patients with hematologic conditions such as sickle cell disease, hereditary spherocytosis, and various hemolytic anemias, or in the immunocompromised.
Recrudescence of the lacy, reticular rash may occur with exercise, overheating, emotional upset, or sun exposure as a result of cutaneous vasodilatation.
Parvovirus B19 is the most common cause of hydrops fetalis. Pregnant mothers of children diagnosed with erythema infectiosum should have their serologic status determined.
In young adults, parvovirus B19 can cause papular purpuric gloves and socks syndrome.
Fifth Disease. Toddler with the classic slapped-cheek appearance of fifth disease caused by parvovirus B19. Note the lacy reticular macular rash on the shoulder and upper extremity. (Photo contributor: Anne W. Lucky, MD.)