pediatrics
Erythema Infectiosum (Parvovirus B19 Infection)
Diagnosis of Erythema Infectiosum
Physical examination with characteristic rash For children with risk factors for complications, viral testing and complete blood count For pregnant patients, antibody measurement and ultrasonography The rash's appearance and pattern of spread are the only diagnostic features; however, some enteroviruses may cause similar rashes. Distinguishing between these viral etiologies is seldom needed for the clinical care of otherwise healthy children. Diagnosis can be ruled out by serologic testing; an exposure history is also helpful. Other childhood exanthems have distinct diagnostic features. Serologic testing is not required in otherwise healthy children; however, children with a known hemoglobinopathy or immunocompromised state should have viral and/or antibody testing as well as a complete blood count (CBC) and reticulocyte count to detect hematopoietic suppression. In children with transient aplastic crisis or adults with arthropathy, the presence of IgM-specific antibody to parvovirus B19 in the late acute or early convalescent phase strongly supports the diagnosis. Parvovirus B19 viremia also can be detected by quantitative polymerase chain reaction (PCR) techniques, which are generally used for patients with transient or chronic aplasia, patients who are immunocompromised, and fetuses or neonates with hydrops fetalis or congenital infection. In pregnant patients, antibodies are measured; IgG suggests immunity due to prior infection (which is usually reassuring) and IgM indicates current or recent infection (which raises concern for potential fetal morbidity). Initial assessment of fetal status is with ultrasonography. 