The invention relates to a refrigerated display case with an illuminated support member or “mullion” that efficiently transfers heat generated by at least one light emitting diode (LED) to warm and maintain door seals. The invention further relates to a low-profile, elongated LED light fixture that is retrofitted to the display case mullion to provide efficient illumination. The LED light fixture includes an elongated frame having a central hub extending longitudinally along the frame. A pair of opposed arms extending upwardly at an angle from the central hub, wherein the terminus of each arm has a curvilinear configuration that defines a receiver. At least one leg extends rearward from the central hub. Two legs are spaced a distance apart to define an elongated central cavity that that receives a fastener for securement of the fixture to the vertical support within the display case. A printed circuit board resides within a channel of the central hub and a plurality of LEDs are electrically and mechanically connected to the circuit board. A substantially planar lens cover resides within the receiver for securement to the frame.