Child health · UKMLA & AKT
Erythema infectiosum (Fifth disease/Parvovirus B19)
A free high-yield preview for the UKMLA Applied Knowledge Test, covering how to recognise this condition. The full SA Note notes add investigations, management and complications, with practice questions on this topic.
Key high-yield points
- Prodrome (infectious phase): low-grade fever, coryzal symptoms, headache, myalgia - child is contagious here, NOT when the rash appears
- 'Slapped cheek' rash: bright red confluent erythema over both cheeks with perioral pallor - appears once child is afebrile and recovering
- Lacy reticular rash: pink net-like maculopapular rash on trunk and limbs, 1-4 days after facial rash; blanching, non-pruritic; may recrudesce with heat/exercise for weeks
- Adults: slapped cheek often absent; dominant feature is symmetrical polyarthropathy (hands, wrists, knees) - can mimic rheumatoid arthritis
The rash is immune-mediated (not direct viral effect) - this is why the child is no longer viraemic and no longer infectious once the rash appears.
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