Contents
Introudction
Fifth Disease – so called as it was the fifth of the six common childhood skin rashes when it was first classified back in the 18th and 19th centuries.
Formally known as Erythema Infectiosum and also colloquially called slapped cheek syndrome.
Aietiology and Epidemiology
- Caused by infection with Parvovirus B19 (aka erythrovirus)
- Most commonly affects
- Incubation period of about 10-18 days
- Once the rash has appeared it is no longer infectious – but will be in the 10 days preceding this
- Very common and very infectious – 60% of adults aged 20 will have already had the infection
- Transmitted via respiratory secretions and droplets in the air
- Can also pass across the placenta – see below for parvovirus in pregnancy
- One infection gives life-long immunity
Presentation
- Erythematous maculopapular rash on the cheeks. Very distinctive – look like child has been ‘slapped’ on the cheeks bilaterally.
- Usually the face rash starts before the limb and trunk rash, but not always
- A reticular (dotty, widespread) rash on the trunk and limbs – often on the legs
- Symptoms usually last 4-5 days but can last up to 3 weeks
- Occasionally will cause joint pains (arthralgia) and fever
- About 25% of cases are asymptomatic
Treatment
- No treatment required in most cases – will resolve without intervention
- In pregnancy – see below. No active treatment in most cases – if hydrops develops then transfusion reduces fetal mortality.
Avoiding transmission
- Symptoms appear after the infectious period so there is no point withholding children from school
- In institutions it can be particularly easily passed on. Thorough hand-washing and avoidance of at-risk groups (pregnant women, immunocompromised and those with RBC disease) is advised
Complications
- Usually none
- Can cause problems in pregnancy (see below)
- Can cause a transient aplastioc crisis as it tends to affect immature red blood cells. This is pretty rare but can occur in those with underlying Red Cell disease(e.g. sickle cell, thalassaemia etc).
In Pregnancy
- Can cross the placenta. Risk of crossing placenta increases with gestation. 0% at <4 weeks and up to 70% at >16 weeks.
- About 40-50% of pregnant mothers will not be immune
- The risk of contracting it from a child with symptoms is about 50%
- About 1:4000 pregnant ladies will ocntract the virus during pregnancy
- Symptoms similar to children including rash, fever and joint pains
- 9% risk of miscarriage if baby <20 weeks gestation
- 3% risk of hydrops fetalis – and half of these babies will die due to anaemia – but the absolute risk is pretty low (about 30 babies/year in the UK)
- You should suspect parvovrius in any pregnant woman with a rash
- Test for parvovirus B19 IgG and IgM
- IgG only – previously infected – immune from parvocirus. Reassure.
- Nil detected – repeat in 1month or if further symptoms develop. If this is negative reassure the woman that she has not been infected, but remind her she is at risk of infection.
- IgM positive (regardless of IgG). Retest immediately to confirm. Advise mother of results and implications. Refer to fetal unit who will monitor (USS at 4 weeks post diagnosis and every 1-2 weeks until 30 weeks gestation) for hydrops. If this develops fetal transfusion can reduce mortality from 50% to 18%. There are no long-term complications whether hydrops develops or not if fetus survives.
