Extragenital scaly skin

They have a purple or lilac colour and the surface shows cigarette-paper wrinkling, rather than the salmon pink colour and thicker scale of psoriasis.

This is extragenital lichen sclerosus. The condition typically presents as an itchy perivulvar rash in females, but this patient had no genital involvement.

Sometimes there is bleeding into the lesions but that is a late feature. The cause is not known but in Europe Borrelia infection has been implicated, with resolution after penicillin.