Parvovirus B19 (slapped cheek disease)

slapped cheek · fifth disease · erythema infectiosum · parvovirus B19 · parvovirus

A well child with red cheeks - harmless in most, but dangerous in pregnancy, immunosuppression and haemolytic anaemia.

GPBand B

Red flags

Sickle cell disease, thalassaemia, hereditary spherocytosis or any chronic haemolytic anaemia - parvovirus B19 causes transient aplastic crisis; check a full blood count and reticulocytes urgently and admit if anaemic
Pregnancy, at any gestation - risk of fetal anaemia and hydrops. CKS applies no gestational threshold: at any stage of pregnancy, virology or infectious diseases should be contacted immediately, and confirmed infection needs urgent fetal medicine referral. Do not let gestation lower the urgency
Immunosuppression - risk of chronic anaemia and prolonged infection
Pallor, breathlessness, tachycardia or lethargy - assume aplastic crisis until the blood count says otherwise

Recognise

On light skin

Striking bright red firm erythema over both cheeks with perioral sparing, then a fine lacy pink reticular rash on the limbs.

On brown and black skin

The slapped-cheek appearance depends entirely on visible redness and is frequently absent or unrecognisable in brown and black skin - the facial finding may be no more than a subtly darker or warmer-toned area over the cheeks, or nothing at all. The lacy, net-like reticular pattern on the limbs is a pattern rather than a colour and is the more reliable sign; look for it in good light across the outer arms and thighs, and feel the warmth and slight induration of the cheeks. Relying on the classic red cheeks will under-diagnose this condition in exactly the populations where sickle cell disease, and therefore aplastic crisis risk, is commonest - which makes this one of the highest-stakes recognition gaps in the band.

In any skin tone

The child is well and often already better by the time the rash appears
Facial change first, the lacy limb rash days later
The limb rash recurs for weeks, triggered by heat, exercise or sunlight - this alarms parents and is not a relapse
By the time the rash is visible the patient is generally no longer infectious
Joint pain, often symmetrical and in the hands, particularly in adult women

Distribution

Bright confluent erythema across both cheeks with sparing around the mouth, followed days later by a lacy, reticular rash on the arms, legs and trunk that comes and goes for weeks with heat or sunlight.

Photographs

Slapped cheek, the classic face of parvovirus B19. Confluent red erythema over both cheeks with sparing of the skin immediately around the m — Slapped cheek, the classic face of parvovirus B19. Confluent red erythema over both cheeks with **sparing of the skin immediately around the mouth** and of the bridge of the nose. The child is otherwise well. On brown and black skin this facial flush may be invisible, and the lacy reticular rash that follows on the limbs a few days later is often the only thing you will see. The only openly licensed photograph found for this entry shows light skin. **That is a limitation of this page, not of the disease** - a darker-skin photograph is still being sought.
Fitzpatrick I (Fitzpatrick type estimated from the photograph, not stated by the source) · Sandyjameslord · Wikimedia Commons - 14 month old with Fifth Disease.jpg · CC BY-SA 4.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Rubella — Both mild with arthralgia; rubella's rash is discrete and it carries a different pregnancy risk
Measles — Measles has a prodrome, a cough and a miserable child; parvovirus has a well child
Acute urticaria — The lacy reticular rash can be mistaken for urticaria, but it does not itch in the same way and is fixed in pattern

What to do in the ED

Ask about haemoglobinopathy in the child and the family, and about pregnancy in every household contact - these two questions carry the entire clinical risk
In any child with a haemolytic condition, take FBC and reticulocytes and treat a falling haemoglobin as an aplastic crisis
In pregnancy, arrange serology and same-day obstetric discussion; do not defer to the GP
Explain that the lacy rash will come and go for weeks with heat and sunlight and does not mean the illness is returning
Exclusion from school is not required once the rash has appeared, because infectivity has usually passed - but a pregnant or immunosuppressed contact still needs advice
No specific treatment in the well child; supportive care only

Disposition

A well child needs no more than explanation and supportive care. Admit or discuss urgently for aplastic crisis, immunosuppression, or fetal concern in pregnancy.

Safety-netting

The lacy rash may come and go for several weeks whenever the child is warm or in the sun - this is expected and not a relapse. Return urgently if the child becomes pale, unusually tired, breathless or short of breath. Tell us if anyone in the household is pregnant, or if the child has sickle cell disease, thalassaemia or another blood condition.

Sources

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