According to some sources The Cathars arise from Bogomilism that was a Gnostic religiopolitical sect founded in the First Bulgarian Empire by the priest Bogomil during the reign of Tsar Petar I in the 10th century: http://en.wikipedia.org/wiki/Bogomilism
"It is a complicated task to determine the true character and the tenets of any ancient religion, considering that almost all the information that has reached us comes from their opponents. Much of the heretical literature has been thoroughly persecuted and burned by the Bulgarian state, the Roman Empire (Byzantine) and the Holy Roman Empire (Western). Some has survived in changed forms in other countries like France or Italy where Bogomilism was spread under the name Catharism."
"The Cathars' beliefs are thought to have come originally from Eastern Europe and the Byzantine Empire by way of trade routes. The name of Bulgarians (Bougres) was also applied to the Albigenses, and they maintained an association with the similar Christian movement of the Bogomils ("Friends of God") of Thrace. "That there was a substantial transmission of ritual and ideas from Bogomilism to Catharism is beyond reasonable doubt." Their doctrines have numerous resemblances to those of the Bogomils and the earlier Paulicians as well as the Manicheans and the Christian Gnostics of the first few centuries AD, although, as many scholars, most notably Mark Pegg, have pointed out, it would be erroneous to extrapolate direct, historical connections based on theoretical similarities perceived by modern scholars.": http://en.wikipedia.org/wiki/Catharism