It is uncommon for scarring, thought to be due to acne, to  be, in fact, present for other reasons.  Occasionally, however,  patients are sent to the clinic with  'acne' scarring but  a better history and  examination and, if necessary, investigation of the patient, may reveal other features.

Conditions to be considered are hydroa vacciniforme, ulerythema oophryogenes, atrophia maculosa varioliformis cutis  and porphyria cutanea tarda.