A catheter is disclosed for performing ultraviolet light therapy in a pulmonary system of a patient, which includes a catheter body having opposed proximal and distal end portions, a handle assembly operatively associated with the proximal end portion of the catheter body, an illumination assembly operatively associated with the distal end portion of the catheter body and including an LED light source for generating UVC radiation, wherein the illumination assembly includes a coupler connecting the LED light source with the distal end portion of the catheter body, and an elongated braided sleeve disposed within the catheter body, wherein the coupler is adapted to transfer heat from the illumination assembly to the braided sleeve, such that the braided sleeve serves as a heat sink for the illumination assembly.