Facial rash in a pregnant woman
Article Outline
Case presentation
A 24-year-old pregnant woman presented to her General Practitioner at 20 weeks gestation. She gave a 5-day history of vague symptoms, consisting principally of epigastric pain and a mild cough. A community pharmacist had noted a facial rash, raised the concern of ‘slapped cheek syndrome’ and advised her to seek medical attention. She was otherwise well and the pregnancy had been uneventful. Rubella IgG had been detected on routine antenatal screening at 12 weeks gestation, and an ultrasound scan at that point had been unremarkable. A current serum sample and the booking serum sample were submitted for parvovirus B19 testing.
Both the booking sample (12 weeks gestation) and current sample (20 weeks gestation) were tested for the presence of parvovirus B19 specific IgM and IgG antibodies (Biotrin International, Dublin, Ireland). The initial booking sample was not initially identified as such and laboratory protocol would have been to test for IgG only on this earlier sample. Both samples had detectable IgG. The 12-week sample was persistently reactive for parvovirus B19 IgM antibodies, but within the equivocal range for the assay. The 20-week sample was negative for parvovirus B19 specific IgM. Parvovirus B19 DNA was detected in the 12-week sample by quantitative PCR at a level of 3.3
×104IU/ml (in house assay performed at Virus Reference Department, CfI).
What is your interpretation of these results?
What further tests are indicated?
Please see evidence-based opinion overleaf.
Evidence-based opinion.
What is your interpretation of these results?
Parvovirus B19 (official abbreviation—B19V) is the aetiological agent of erythema infectiosum, also known as fifth disease or slapped cheek disease due to the characteristic facial rash often seen in children with infection.1 The illness can be difficult to diagnose on clinical grounds alone, but the diagnosis is readily made by the detection of specific parvovirus B19 IgM in serum samples.2 Although earlier assays based on B19V antigens expressed in E. coli lacked specificity, the current ELISA assays based on recombinant viral-like particles expressed in yeast or insect cells are highly predictive (good sensitivity and specificity), although weakly reactive IgMs due to cross-reactivity are not uncommon.3 With the more sensitive assays now available, B19V IgM is detectable within 1 day of rash onset.
Confirmation of IgM results could be carried out by using epitope based avidity assays, or increasingly by quantitative B19V DNA.4 Although in acute infection, B19V DNA titres of >1012IU/ml (1IU is ∼1 genome copy, and quantitative assays should be validated against the WHO B19V DNA standard available from NIBSC, South Mimms, Potters Bar, UK) can be detected, these high levels drop within 2–3 days to about 106IU/ml and slowly drop to 104IU/ml over the next 2–3 months5 (personal unpublished data). Levels of >104IU/ml can then persist for months to years even in healthy individuals.6, 7
Although B19V infection in children and adults is generally a mild infection with no long term sequelae, infection during pregnancy can lead to increased fetal loss, development of hydrops fetalis8 and rarely may lead to congenital anaemia in the fetus.9 The greatest risk of fetal abnormality is in the mid trimester, and current UK guidelines recommend that pregnant women with a rash illness compatible with rubella or parvovirus B19 in the first 20 weeks of pregnancy should be investigated.10
The risks of B19V infection within the first month of pregnancy are not clearly known. Although rare case reports suggesting congenital abnormalities following maternal B19V infection at a very early stage of pregnancy are in the literature,11 they have not been well documented, and this has not been observed in any of the controlled studies of B19V infection in pregnancy. However, an increased rate of fetal loss due to B19V infection at this stage of pregnancy cannot be excluded.
20-week sample: B19V IgM negative and IgG positive. These results are consistent with previous B19V infection. The absence of IgM at the time of the rash indicated that B19V infection is not the cause of the facial rash.
12-week sample: B19V IgM equivocal and B19V DNA 3.3×104IU/ml. Although the B19V IgM is equivocal, the level of B19V DNA is consistent with previous infection, or at least with infection >2–3 months earlier.
What further tests are indicated?
No further tests are required for the possible B19V infection. Rubella and B19V infections are virtually indistinguishable clinically, and therefore infection/re-infection with rubella cannot be excluded. According to the UK guidelines,10 Health Protection Agency website (http://www.hpa.org.uk) and best practice, laboratory investigations for rubella infection/reinfection should be initiated irrespective of past testing or immunisation. Depending on the history/illness testing for other viruses causing rash-illness (such as measles) may be appropriate.
Conflict of interest
No conflict of interest for the authors in relation to this article.
Financial support
No financial support.
References
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PII: S1386-6532(09)00378-3
doi:10.1016/j.jcv.2009.08.001
© 2009 Elsevier B.V. All rights reserved.
