Dr Oliver Starr does us a service by drawing our attention to this interesting condition in the case of an 11-year-old girl with a rash.
He has given a classic description of Pityriasis rosea – red, discrete lesions of variable size and shape including ovoid and some being scaly – resembling ringworm.
Typically there is a single lesion at the start (the herald patch) followed a week or so later by the appearance of successive lesions. The herald patch may have gone unnoticed by the patient until pointed out by the practitioner (it is often darker than the newer lesions). It may also be mistaken for ringworm (I own up – it was my first case of P. rosea seen as a trainee). Itch is said to be absent in a quarter of cases but I have seen more cases that were not itchy than that were. The condition is more common in older children and young adults.
The cause is unknown
but a viral infection is suspected since it occasionally occurs in association with an upper respiratory tract infection. I recall seeing clusters of cases, which would fit in with an infective aetiology. The condition is self-limiting though I have had some cases go on for up to three months.
Further details on the condition can be found at emedicine – www.tinyurl.com/ 353s57h. And some good photos can be seen at dermnet.nz – www.tinyurl.com/2ueaafj.
Response to: What are these lesions on this girl’s back?
From Dr Kevork Hopayian, Leiston, Suffolk