Erythema infectiosum (parvovirus B19)

What it is

Erythema infectiosum, also called fifth disease or slapped-cheek syndrome, is caused by human parvovirus B19, a DNA virus identified in the 1980s as the cause of erythema infectiosum. It is called fifth disease because it is the fifth of the five viral rash diseases of childhood to be described, the other four being measles, rubella, chicken pox and roseola.

It is relatively common and mildly contagious, appears sporadically or in outbreaks, in children between 5 and 14 years of age; a second table gives the age band as 5-15 years. The incubation period is 13 to 18 days, and asymptomatic infection is common.

How it presents

Erythema infectiosum is the most common presenting illness of parvovirus B19. The systemic symptoms are lethargy, fever and headache, though the prodrome is reported two ways: in one it is none, with fever often absent or low grade, and in the typical history it is a mild cold in the week before, reported by the mother. Fever and other symptoms may be present but are uncommon.

The eruptive phase has three distinct, overlapping stages:

• Facial erythema, the slapped cheek: bright red macules on both cheeks, erythematous and maculopapular, described elsewhere as an erythematous malar blush
• Reticular erythema of the shoulder: a lacy, reticular eruption on the extremities and torso, following the slapped cheeks in 1 to 4 days; an erythematous maculopapular eruption on the extensor surfaces of the extremities that evolves into a reticulated, lacy, mottled appearance; the slapped-cheek rash also spreads to the proximal arms and extensor surfaces
• Recurrent phase: the eruption may fade and then reappear in previously affected sites on the face and body during the next 2 to 3 weeks

The rash is also put as an erythematous, pruritic, maculopapular rash that starts on the arms and spreads to the trunk and legs, worsening with fever and sun exposure. The lacy reticular rash on cheeks and upper body spares the palms and soles.

One point separates it from the other red faces: in the slapped cheek of parvovirus B19 the nose is spared, unlike the malar rash of SLE and unlike the malar flush of mitral stenosis and polycythemia vera, a vasomotor reaction with no true skin lesions.