A rare and incurable neurodegenerative disorder can make you laugh till you die. This disease is caused by prions and is also known as Kuru. Kuru, this condition was common among the Fore people of Papua New Guinea.  The Kuru term is derived from the foreword Kuria, meaning shaking, because of the body tremors that are a classic sign of this disease. It causes uncontrollable tremors, and a patient is prone to pathologic bursts of laughter.  And there is no cure for this disease.