The structure of the outskirts of galaxies provides valuable information about their past and evolution. Due to their projected orientation edge-on isolated galaxies effectively serve as test labs in which to study the three-dimensional structure of galaxies, including warps and flares, and to explore the possible sources of such distortions. We analyzed the structure of the apparently isolated edge-on ultra-thin galaxy UGC 11859 to look for the presence of distortions. The deep optical imaging observations ( surf. bri. lim. = 30.6 and 30.0 mag arcsec-2 in the g and r bands respectively) we acquired with the 10.4m Gran Telescopio Canarias (GTC) are used to derive the radial and vertical surface brightness profiles and the g-r color profile. We find that the disk of UGC 11859 displays a significant gravitaional distortion. A warp is clearly detected on one side of the disk, and the galatic plane on both sides of the center shows increasing scale height with increasing galacticentric radius, indicating the presence of a flare in the stellar distribution. The surface brightness profile of the disk shows a sharp break at 24 kpc galactocentric radius and a steep decline to larger radii, an "edge-on truncation" which we associate with the presence of the flar. the present study the first observational support for a connection between truncations and flares.Just beyond the waroped side of the disk a faint galaxy is observed within asmall angular distance, identified as a potential interacting companion, Based on ultra-deep g and r photometry we estimaate that if hte potential companion is at the same distance as UGC 11859 the stellar mass is 6.33 (+- 0.02) in units of logarithmic solar mass.