Pityron is Greek word for bran. The pityriases are skin diseases characterised by fine, bran-like scales. Pityriasis rosea is an acute, self-limiting condition with scaly oval papules and plaques mainly occurring on the trunk.
The cause is unknown, human herpes virus 7 has been suggested; however, the virus is not always detectable in patients with pityriasis rosea.
Most cases commence with a herald patch, a single salmon pink lesion 2–5 cm in diameter with central clearing and peripheral scaling. Days later crops of similar smaller oval plaques appear and proximal extremities. The lesions distribute along dermatomal lines, which is most evident on the back appearing in a ‘Christmas tree’ pattern.
Steroids and phototherapy may be of value for associated itching.
Self-limiting. The condition fades in 1–2 months.