Fifth disease is a common childhood viral illness that poses a threat of few sequelae in the healthy child. However, the infection can masquerade as other disorders in patients of all ages, leading to misdiagnosis, failure to diagnose, and, at times, overtreatment. Clinician awareness of the many “costumes” worn by this viral infection is key to improved diagnosis and treatment for patients with the disease.
What do these presentations have in common? A 52-year-old, generally healthy white male schoolteacher presents with new-onset symmetric joint pain localized to the hands and wrists for the past 3 to 4 weeks. He has also experienced profound fatigue for 6 to 7 weeks.
A 31-year-old female presents with facial rash, fever, arthropathy, and myalgia. Initial laboratory test results indicate cytopenia, hypocomplementemia, anti-DNA, and antinuclear antibodies (ANAs).
A 36-year-old, gravid pediatric nurse in her third trimester notes an absence of fetal movement 1 week after having a mild flulike illness.
A 50-year-old male presents with the classic signs and symptoms of acute MI with normal cardiac angiography. He later develops left ventricular dysfunction (LVD).
HISTORICAL PERSPECTIVE
Fifth disease, another name for erythema infectiosum (EI), follows measles, scarlet fever, rubella, and Filatov-Dukes disease in the classification of common childhood exanthems (70% of patients are age 5 to 15 years) and is caused by the parvovirus B19 (B19).1,2 In 1975, Yvonne Cossart, an Australian virologist, noted an anomalous reaction of normal blood donors' sera corresponding to position 19 in an assay for hepatitis B, thus identifying the first parvovirus of human blood.3 Eight years later, investigators found a connection between the human parvovirus and EI;4 10 years after that, they determined that viral replication occurs only in erythroid progenitor cells, specifically to the blood-group P antigen.5 Distinct B19 syndromes are widespread, and known manifestations are seen in pediatrics, obstetrics, dermatology, rheumatology, and hematology.6
ETIOLOGY AND EPIDEMIOLOGY
B19, a single-strand, nonenveloped DNA virus that contains two capsid proteins (VP1 and VP2) and one nonstructural protein (NS1), is an erythrovirus that infects only mammals.7 B19 infection is common throughout the world. Outbreaks are observed in late winter or early spring. Viral transmission occurs via inhalation of infected droplets or transfusion of infected blood products and vertically from mother to fetus. Incubation ranges from 4 to 14 days and up to 21 days. The transmission rate is about 50% for household exposures and approximately 20% to 30% for susceptible teachers and daycare workers.1,7-10 B19 infection among health care workers supports transmission within and across patient wards via common staff areas and handling contaminated materials.11 However, one hospital outbreak demonstrated the ease of community-acquired infection when the rate of infection among medical students who had been exposed while in hospital attendance was lower (33.6%) than that of students who had not been in hospital attendance (42.6%).12
CLINICAL MANIFESTATIONS
Classic childhood B19 infection manifests as rash with the distinctive appearance of a slapped cheek or facial flush following a low-grade fever, coryza, headache, and nausea. The infection completes its course with a diffuse macular, lacy, reticulated-appearing rash on the trunk and extremities. The rash can be exacerbated by sunlight, heat, exercise, and stress for up to 3 weeks. The infection ultimately resolves spontaneously, leaving the child with lifelong immunity. Children often recover without sequelae; 85% of the elderly show seropositivity. Older children may experience mild pruritus; lymphadenopathy; and atypical papular, purpuric, or vesicular rashes.1,7,8 However, less common childhood and adult manifestations, such as those presented by the four patients previously described, can occur.