Erythema Infectiosum

Key Features

Essentials of Diagnosis

• Fever and rash with "slapped-cheek" appearance, followed by a symmetric, full-body maculopapular rash

• Arthritis in older children

• Profound anemia in patients with impaired erythrocyte production

• Nonimmune hydrops fetalis following infection of pregnant women

General Considerations

• Benign exanthematous illness of school-aged children

• Caused by the human parvovirus B19

• A nonspecific mild flulike illness may occur during the viremia at 7–10 days

• Characteristic rash that occurs at 10–17 days represents an immune response

• Patient is viremic and contagious prior to—but not after—the onset of rash

• Transmission is via respiratory secretions, occurring in winter–spring epidemics

Demographics

• Most cases (60%) occur in children between ages 5 and 15 years, with an additional 40% occurring later in life

• Forty percent of adults are seronegative

• Secondary attack rate in a school or household setting is 50% among susceptible children and 20–30% among susceptible adults

Clinical Findings

Symptoms and Signs

• Typically, the first sign of illness is the rash

  • Begins as raised, fiery red maculopapular lesions on the cheeks that coalesce to give a "slapped-cheek" appearance

  • Lesions are warm, nontender, and sometimes pruritic

  • Nearly 50% of infected children have some rash remaining (or recurring) for 10 days

  • Fine desquamation may be present

• Mild low-grade fever, malaise, sore throat, and coryza occur in up to 50% of children

• Purpuric stocking-glove rashes, neurologic disease, and severe disorders resembling hemolytic-uremic syndrome have also been described

Differential Diagnosis

• In children immunized against measles and rubella, parvovirus B19 is the most frequent agent of morbilliform and rubelliform rashes

• The characteristic rash and the mild nature of the illness distinguish erythema infectiosum from other childhood exanthems

• It lacks the prodromal symptoms of measles and the lymphadenopathy of rubella

• Systemic symptoms and pharyngitis are more prominent with enteroviral infections and scarlet fever

Diagnosis

• Mild leukopenia occurs early in some patients, followed by leukocytosis and lymphocytosis

• IgM antibody is present in 90% of patients at the time of the rash

• Nucleic acid detection tests are often definitive, but parvovirus DNA may be detectable in blood for prolonged periods

Treatment

• Pregnant women who are exposed to erythema infectiosum or who work in a setting in which an epidemic occurs should be tested for evidence of prior infection

• Susceptible pregnant women should then be monitored for evidence of parvovirus infection

• Approximately 1.5% of women of childbearing age are infected during pregnancy

• If maternal infection occurs, the fetus should be monitored using ultrasonography for evidence of hydrops and distress

• Intramuscular immunoglobulin is not protective

• High-dose IVIg has stopped viremia and led to marrow recovery in some cases of prolonged aplasia

Outcome