CHILDHOOD EXANTHEMS: Erythema Infectiosum

Exanthems are a common cause of generalized rashes in children. They pose a diagnostic challenge to even the most experienced physician because of the diversity of their clinical presentations. The morphology distribution, and associated signs and symptoms are sometimes specific enough for a definitive diagnosis, but, nonspecific clinical findings often make this impossible. Advances in laboratory techniques (particularly in viral diseases), new antiviral drugs and vaccines, epidemics of old exanthems, and the recognition of new clinical syndromes have stimulated renewed interest in exanthems.

Historically, exanthems were numbered in the order in which they were first differentiated from other exanthems. Thus, "first" disease was measles (rubeola), "second" disease was scarlet fever, and "third" disease was rubella (German measles). The specific disease described as "fourth" disease, so-called Pilatov-Dukes disease, is no longer accepted as a distinct clinical entity, with some authors speculating that it represented staphylococcal scalded skin syndrome, and others speculating that it was concurrent infection with both scarlet fever and rubella. Fifth disease is erythema infectiosum, and sixth disease is roseola infantum. Only in the last decade, with the identification of parvovirus B19 as the cause of erythema infectiosum and human herpesvirus 6 as the cause of roseola infantum, have the causative agents of the classic exanthems been identified.

Erythema Infectiosum (Fifth Disease)

Introduction

Fifth disease is a disease that resembles measles in that it, too, is caused by a virus and causes a rash. The fifth such disease to be recognized (after measles, German measles, chickenpox, and roseola), the cause has been discovered to be human parvovirus B19, and this disease is also known as "erythema infectiosum" (a rash of infection). The incubation period is 4 to 12 days and the illness itself is usually mild, with low grade fever, slight malaise, and a typical blotchy rash that provokes a "slapped face" appearance over the cheeks, before spreading to the rest of the body, arms, and legs. The condition lasts for from 5 to 10 days, but the rash can reappear over a period of several weeks, particularly after exposure to bright sunlight, after exercise, following a hot bath or shower, or even during emotional distress. When the infection strikes adults, as it may do on occasion, mild joint pain and swelling may sometimes be experienced. Fifth disease breaks out most frequently during the spring months and is common in children and adolescents. Special precautions to isolate pregnant women from this infection are necessary, as fetal abnormalities have been reported in women who become infected during their first three months of pregnancy. While blood serology tests exist to establish the diagnosis, the appearance and location of the rash generally suffices to make the diagnosis. As yet there are no immunizations available, and the only treatments available or necessary are those simple procedures necessary to keep the patient comfortable during this mild illness.

What causes it? Erythema infectiosum is caused by human parvovirus B19 infection. This virus is also recognized as a cause of transient aplastic crisis in patients with hemolytic anemias and hemoglobinopathies, chronic anemia in immunodeficient patients, and an arthritis similar to rheumatoid arthritis as well as intrauterine infection and fetal death in infected pregnant women. The virus can affect all age groups, but the classic exanthem, erythema infectiosum, is most common in school-aged children ages 5 to 15. The incubation period is usually between 4 and 14 days but may last as long as 20 days. The disease is transmitted by respiratory secretions.

How does it begin? The incubation period of erythema infectiosum is typically between 4 and 14 days, after which 20% to 60% of persons have a mild prodromal illness. In a study of human volunteer subjects, four of the seven adult subjects had mild fever (less than 37.8 degrees C), headache, pruritus, malaise, and chills 8 to 10 days after inoculation that lasted for 1 to 4 days. The second phase of illness, characterized by the rash and a low-grade fever, began approximately 1 week later.

How does it progress? The characteristic exanthem of erythema infectiosum occurs in three overlapping phases. The initial phase is that of an erythematous, raised, and warm rash, prominent over the eminences of the face and often associated with a circumoral pallor. It is referred to as the "slapped cheek" rash and is rarely present in the infected adult. This eruption generally fades in 3 to 5 days. The second phase begins concurrently with the first or up to 5 days later. This symmetric rash becomes most prominent on the extensor surfaces of the extremities and on the buttocks. It may involve the palms and soles. It is characteristically a mildly pruritic, macular, and papular eruption, which clears centrally as it progresses, forming a reticular or lacy pattern. During the third and final stage, the rash may wax and wane. Recrudescence is often associated with sunlight, bathing, exercise, and traumas. Resolution of the rash is typically complete in 1 to 2 weeks. Post inflammatory hyper pigmentation may occur. These dark spots will fade in time.

How is it diagnosed? Fifth disease can be verified by identification of viral particles or by a blood test. Viral particles can be detected by counter-immunoelectrophoresis (CIE) or by the more sensitive DNA hybridization technique in serum, urine, and respiratory secretions during the prodrome. IgG and IgM parvovirus antibodies can be measured by radioimmunoassays or enzyme-linked immunoabsorbent assays. The presence of IgM antibody, or a fourfold increase of IgG antibody indicate a current infection with parvovirus. IgM remains in the serum for approximately 2 months after primary infection whereas IgG persists for years. Furthermore, the finding of IgG is evidence of immunity infection.

How is it treated? In the otherwise healthy person, no treatment is necessary for self-limited erythema infectiosum. Aplastic crisis resulting from parvovirus infection typically lasts 10 to 12 days and may require transfusions. The arthritis, common in infected adults and less common in children, responds to anti-inflammatory therapy. At present there is no vaccine to prevent infection with parvovirus. Patients with fifth disease are contagious before the rash develops therefore, for susceptible people such as pregnant women and persons with chronic hemolytic anemias, avoidance of persons with viremia is difficult. If an outbreak of erythema infectiosum occurs in a school, it is advisable that all pregnant personnel remain at home for 2 to 3 weeks after the last case has been diagnosed.