Fifth Disease or Erythema Infectiosum
- Author: Kenneth T Kwon, MD; Chief Editor: Richard G Bachur, MD more...
Background
Erythema infectiosum is usually a benign childhood condition characterized by a classic slapped-cheek and lacy exanthem. It is an infection caused by human parvovirus (HPV) B19. Human parvovirus B19 also is associated with other hematologic, rheumatologic, and neurologic conditions, including polyarthropathy, aplastic anemia, and hydrops fetalis.
Classic slapped-cheek appearance of fifth disease. Pathophysiology
Human parvovirus B19, a member of the family Parvoviridae, is a heat-stable, single-stranded DNA virus. Human parvovirus B19 was accidentally discovered in 1975.[1] It is the only parvovirus known to cause disease in humans. Transmission occurs through respiratory secretions, possibly through fomites, and parenterally via vertical transmission from mother to fetus and by transfusion of blood or blood products.
Anderson et al described the pathophysiology of the virus by studying human volunteers who had been inoculated with the virus.[2]
The incubation period is usually 7-10 days, but it can be 4-21 days. The mechanism producing the dermatologic and rheumatologic features is unknown but thought to represent antigen-antibody (Ag-Ab) complexes in the skin and joints.
Arthropathy is observed most commonly in adult women and occurs in fewer than 10% of children. It is a symmetric polyarthritis, usually involving finger joints. The onset of joint symptoms occurs 2-3 weeks after exposure.
The association of human parvovirus B19 and aplastic anemia is thought to be due to the affinity and cytotoxicity of the virus for erythroid progenitor cells. This complication is primarily observed in patients with underlying hemolytic anemias (eg, sickle cell disease, thalassemia) or immunodeficiency states (eg, leukemia, HIV). These disease states depend on high red-cell production, due to shortened cell life span. The hematocrit of these patients may drop as much as 10-15% per day during acute infection. Most patients have a human parvovirus B19 aplastic crisis only once, and a rash following aplastic crisis is rare.
Previously healthy patients also develop transient (and usually clinically insignificant) bone marrow suppression and reticulocytopenia. In rare cases, mild lymphopenia, neutropenia, and thrombocytopenia also may occur.
Fetal transmission may result in severe anemia with resultant congestive heart failure and fetal hydrops. This occurs in fewer than 10% of primary maternal infections. Recent studies report 1-9% risk of fetal death in pregnant women exposed to active human parvovirus infection, with greater risk of fetal loss in early pregnancy. Approximately one half of women of childbearing age are seropositive; therefore, they are immune and are of no risk to the fetus. No evidence suggests specific congenital malformations due to in-utero exposure to human parvovirus B19.
An association between human parvovirus B19 infection and encephalitis, neuropathies, myocarditis, nephritis, systemic lupus erythematosus (SLE), Henoch-Schönlein purpura (HSP), and rheumatoid arthritis has been described. Many of these associations have not been validated.
Epidemiology
Frequency
United States
Sporadic cases occur, but outbreaks are more common. Up to 60% of the population is seropositive for anti-HPV B19 immunoglobulin G (IgG) by age 20 years. The incidence peaks in winter and early spring.[3] Human parvovirus B19 epidemics appear to occur in cyclical fashion every 4-7 years and are estimated to affect 30-50% of US households. Community epidemics usually last 3-6 months. Subclinical infections are common.
International
The disease occurs worldwide, especially in temperate climates. Anti-parvovirus IgG is found equally among Americans, Asians, and Europeans.[4]
Mortality/Morbidity
Arthropathy is observed in fewer than 10% of children with fifth disease. Incidence of human parvovirus B19-induced aplastic crisis in patients with chronic hemolytic anemia is 2-5% per year. Very rarely, children may develop elevated liver transaminases or self-limited hepatitis.[4]
Sex
Females are affected slightly more often than males.
Age
Approximately 70% of total cases occur in children aged 5-15 years. Infants and adults are affected infrequently.
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