A hinge assembly for a mullion assembly includes a first hinge element having a first cam member with a cammed upper surface having a first portion and a second portion with an angled intermediate portion disposed therebetween. The first portion of the cammed upper surface of the first hinge element is vertically spaced-apart a distance from the second portion. A second hinge element is rotatably coupled to the first hinge element between first and second positions and includes a second cam member having a cammed lower surface that includes an engagement point that is engaged with the cammed upper surface of the first hinge element. The second hinge element is driven upwardly by the engagement of the engagement point and the cammed upper surface of the first hinge element as the second hinge element is rotated from the first position to the second position.