Erythema infectiosum is a common viral illness due to parvovirus B19 that typically occurs in the late winter and spring among school-age children.

Parvovirus B19, a single-stranded DNA virus of the Parvoviridae family, is transmitted from person to person through respiratory secretions.

The incubation period lasts 4 to 14 days, but it may be as long as 3 weeks.

Some patients experience a mild prodrome of low-grade fever, malaise, upper respiratory symptoms, or headache 2 days before the onset of the rash.

Typically the exanthem of erythema infectiosum progresses through following three phases:

1. First is the characteristic bright red facial erythema involving the malar surfaces classically sparing the nasal bridge, periorbital, and perioral areas resulting in the so-called “slapped cheeks” appearance (Fig. 7.4).

2. One to 4 days later, a lacy, reticular erythematous exanthem composed of discrete macules and papules on the extensor surfaces of the extremities appears and later spreads to the trunk and buttocks (Fig. 7.5A,B). The palms and soles are usually spared.

3. The third phase occurs in only some patients and is characterized by periodic recrudescence of the reticular erythema in response to physical stimuli such as heat, friction, sunlight, or warm baths.

Some children may experience mild joint pain that resolves within several weeks but occasionally can persist for several months.

Parvovirus B19 infection can be associated with a symmetric polyarthropathy, involving the hands, feet, elbows, and knees usually affecting adult women.

Infection with parvovirus B19 can also present as papular-purpuric gloves and socks syndrome (PPGSS), which is characterized by painful erythema, petechiae, and purpura involving the palms and soles, occurring most often in older children and young adults.

PPGSS may be associated with a mild prodrome and an enanthem. Therapy is symptomatic and spontaneous resolution occurs in 1 to 2 weeks.

The diagnosis is based on the characteristic clinical presentation.

Although usually unnecessary, serologic detection of parvovirus B19 IgM as soon as 3 days after the onset of the exanthem can confirm recent infection.

Specific IgM antibodies persist for 2 to 3 months after acute infection.

Due to its affinity for red blood cell precursors, parvovirus B19 infection during pregnancy can lead to varying degrees of fetal anemia and is associated with a 4.2% to 9% risk of hydrops fetalis and fetal death. Risk is greatest with infection during the first 20 weeks of pregnancy.

In patients with sickle cell disease, hereditary spherocytosis, and thalassemia intermedia, parvovirus B19 infection can lead to aplastic crises.

Infected immunocompromised patients are at risk of chronic red cell aplasia or generalized bone marrow failure.