AKT · Child health/Infection & rash

Slapped cheek (erythema infectiosum)

Parvovirus B19

Overview

Fifth disease — a mild parvovirus B19 exanthem with bright "slapped cheek" facial erythema then a lacy rash. Important for its complications: fetal hydrops in pregnancy, aplastic crisis in haemolytic anaemia, and chronic anaemia in immunocompromise.

Recognise

Mild prodrome → bright red "slapped cheek" facial rash
Then a lacy/reticular rash on limbs/trunk, recurring with heat/exercise
Often well; arthralgia in older children/adults

Red flags

Pregnancy exposure (fetal hydrops/anaemia); sickle cell/hereditary spherocytosis (APLASTIC crisis); immunocompromised (chronic anaemia)

Differentials & how to tell them apart

Roseolahigh fever THEN rash as the fever breaks (HHV-6)

Rubellapink rash + suboccipital nodes

Scarlet feversandpaper rash + strawberry tongue, needs penicillin

Measlesunwell, Koplik spots, rash with fever

Investigations

Clinical. Parvovirus B19 serology/PCR if pregnant, immunocompromised, or in a haemolytic-anaemia patient.

Management

Supportive; assess pregnancy/haemolysis/immunocompromise risk

1Supportive care; the child is usually no longer infectious once the rash appears.Gate: Exposure in pregnancy, or a child with sickle cell/spherocytosis → check serology/FBC: risk of fetal hydrops or APLASTIC crisis
2Pregnant contact: serology + fetal monitoring; haemolytic patient: monitor for aplastic crisis (may need transfusion).

Supportive — self-limiting; no antiviral

Key points

Parvovirus B19 infects red-cell precursors → aplastic crisis in haemolytic anaemias and fetal hydrops in pregnancy. Infectivity has usually passed by the time the rash appears.

Monitor & prognosis

Resolution; pregnancy/haemolysis follow-up where relevant.

Excellent in the well child; risk lies in the special groups.

Source: NICE CKS Parvovirus B19; RCOG (pregnancy)