Roger is 35 years old and has noticed a skin rash over the last few days. It is mainly on his neck and trunk and is not itchy. Last night, his wife also noticed a larger salmon coloured circular lesion on his lower back. He is otherwise well in himself and has no previous dermatological history. Roger has not used any new creams or washing powder or spent any time in the sun.
Examination reveals a widespread symmetrical maculopapular rash with collarette scaling. The larger patch identified by Roger’s wife is like the other lesions but larger (5cm diameter).
What is the most likely diagnosis?