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Pediatrics, Fifth Disease or Erythema Infectiosum

Author: Kenneth T Kwon, MD, Director of Pediatric Emergency Medicine, Associate Clinical Professor, Department of Emergency Medicine, University of California at Irvine Medical Center; Co-Director, Pediatric Emergency Services, Mission Regional Medical Center/Children's Hospital of Orange County at Mission
Contributor Information and Disclosures

Updated: Mar 19, 2009

Introduction

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.

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; it is the only parvovirus known to infect 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.

The incubation period is usually 7-10 days but 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. 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.

Associations of human parvovirus B19 infection include encephalitis, neuropathies, myocarditis, nephritis, systemic lupus erythematosus (SLE), Henoch-Schönlein purpura (HSP), and rheumatoid arthritis. The exact role of HPV B19, if any, in these diseases is unclear.

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.¹ 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.

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.

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.

Clinical

History

Erythema infectiosum is usually a biphasic illness.

• Mild prodromal symptoms begin approximately 1 week after exposure and last 2-3 days.
  • Headache (20% of pediatric patients)
  • Fever (20%)
  • Sore throat (15%)
  • Pruritus (15%)
  • Coryza (10%)
  • Abdominal pain (10%)
  • Arthralgias (10%)
  • The symptoms above occur more frequently in adults than in children, especially joint symptoms (up to 50%).
• These symptoms precede a symptom-free period of about 7-10 days, followed by a typical exanthem that occurs in 3 phases.
  • Phase 1: A bright red, raised, slapped-cheek rash with circumoral pallor develops.² The nasolabial folds are usually spared.
  • Phase 2: This phase occurs 1-4 days later and is characterized by an erythematous maculopapular rash on proximal extremities (usually arms and extensor surfaces) and trunk, which fades into a classic lace-like reticular pattern as confluent areas clear.² The palms and soles usually are spared.
  • Phase 3: Frequent clearing and recurrences for weeks, and occasionally months, may be due to stimuli such as exercise, irritation, or overheating of skin from bathing or sunlight.

• The rash is often pruritic, especially in adults.
• Enanthems are virtually never observed.
• The rash is observed in approximately 75% of human parvovirus B19 – infected pediatric patients but in less than 50% of infected adults.
• The patient is no longer infectious when the rash appears. Patients with aplastic crisis continue to be viremic and infectious until RBC recovery occurs.

Physical

• Look for involved arthritis.
• In decreasing order of frequency, site of involvement are the following:
  • Metacarpophalangeal and/or interphalangeal areas
  • Knees
  • Wrists
  • Ankles

Causes

• Human parvovirus B19 is the cause.
• Complications of parvovirus infection are observed in patients with underlying chronic hemolytic anemias, congenital or acquired immunodeficiency states, and pregnancy.

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