Abstract: Back-support device providing for expansion of a surface contour of a backrest of a seat, bed, lounge, or other type of body support device. The device includes a back-support that is arranged in the backrest and is made of a pleated fabric. A line of top-stitching is stitched through each fold that forms the pleats. An expandable device such as an air bladder is embedded in the backrest and the back-support device is arranged in the backrest between the air bladder and an occupant of the backrest. The pleats of the back-support device expand outwardly from the backrest, so that the back-support device presses against the back of the occupant, in response to pressure applied by the air bladder. The configuration of the pleats allows the back-support device to readily adapt to the particular contour of the occupant.