A medical appliance, in particular an apparatus for extracorporeal blood treatment, has a housing including a door and with a handle mechanism arranged at the door, via which the door can be locked with the housing via a locking mechanism. A part of the locking mechanism is formed at the handle mechanism in a part thereof that protrudes into the housing. A form-fit unit includes at least one form-fit element and at least one form-fit element counterpart, such that on locking and/or closing the door, the at least one form-fit element at least partly engages in the at least one form-fit element counterpart.