A quick spot-diagnosis quiz for this common childhood presentation.
A 4 year old child is sent home from daycare with a bright red facial rash on the cheeks. He has been otherwise well, although his mother reports that several other family members had cold symptoms a couple of weeks ago. On examination he is active and alert, well hydrated, afebrile, with an unremarkable ENT and cardiorespiratory examination. Apart from the facial erythema, he has no other rashes. Here’s a picture:
1. What is the diagnosis?
2. When can he return to daycare?
3. His mother is also your patient. What would you tell her if she was 15 weeks pregnant? What about 25 weeks pregnant?
4. What is your subsequent management of her pregnancy?
Answers and discussion invited below. Stay tuned for my response next week.
Thanks to all who commented on the case in the comments below or via direct message. Answers and discussion:
1. Yes I agree! It’s almost certainly parvovirus B19 / slapped cheek syndrome / erythema infectiosum / fifth disease. The clue here is the otherwise well child with an absence of other signs and symptoms. Also – the recent viral symptoms in family members may be a clue.
Keep in mind the differentials for facial erythema including different forms of dermatitis, rosacea, psoriasis, sunburn (!), lupus, erysipelas, keratosis pilaris rubra, etc.
2. Parvovirus viraemia begins about 6 days after infection and lasts for a week or so. The appearance of the rash correlates with formation of IgM antibodies and probably represents an immune mediated response, so by this time the infectious period has generally passed and kids don’t need to be isolated.
3. Up to 60% of pregnant women are immune to the virus, and the risk of infection in non-immune women is around 50% for household contact, 20-30% for women exposed in a school or childcare setting and <20% for other community contacts. If the mother is infected, the risk of transmission to the fetus is around 50%.
Parvovirus infection is usually very benign in immuno-competent people, but can result in fetal loss in the unborn child and this risk is significantly higher if transmission occurs before 20 weeks gestation (14.8% vs 2.3% in a pooled analysis of published data, see here, although note that the risk of fetal loss from other causes is also much higher in the first trimester so the loss attributable to parvovirus is more like 5-10%). Fetal hydrops can also occur although the risk is lower at 1%. There doesn’t seem to be an increased risk of congenital malformations.
4. Management of the pregnant woman with exposure to parvovirus involves:
- Checking for immunity with parvovirus serology. IgG positive and IgM negative indicates immunity and suggests no need for further testing. IgG negative and IgM positive indicates recent infection. IgG and IgM negative indicates a patient susceptible to infection and serology can be repeated in 2-4 weeks to look for rising IgG titres.
- Patients who are confirmed as acute infection during the pregnancy are usually screened with 1-2 weekly ultrasound scan for 6-12 weeks after maternal infection. If there are signs of fetal anaemia such as an increased MCA peak systolic velocity, or fetal hydrops such as ascites, pleural or pericardial effusion, then a referral to a tertiary centre for management is warranted.
- Check local protocols or speak to your friendly maternal fetal medicine specialist for further advice!