could u please post a photo..psoriasis usually doesn't appear on the skin folds, but when it appears it is called Inverse Psoriasis, which is uncommon.
Is it itchy? do u have it on other parts of the body, be specific,
does it come and go ?
How old r u? how long r u having this problem for? any changes during seasons ( winter or summer)
Does it bleed when u scratch?
Do other family members have this condition?
Please reply to this questions so we could help you confirm.