The portal administrator can define custome custom fields for the User object. This means that all the portal users can declare some values for these system-wide custom user attributes. This is very usefule in PAC user story. For example the x country portal administrator can define custom fields for all the registered users according to the InternationalSearch_[Country].xml with an one to one mapping.
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Below are some screenshots of the administration control panel that this can be achieved
From the menu Actions -> Permissions you can configure which role will have access to these custom fields. So you can define the patient role for these custom fields