What is itachi sickness?

Itachi, a character from the anime/manga series Naruto, was suffering from a terminal illness called Uchiha clan's kekkei genkai. This illness caused him to slowly lose his eyesight and eventually go blind. In order to prolong his life and protect his younger brother Sasuke, he made a deal with the Akatsuki organization to join them in exchange for sparing his village and family. Itachi's sickness was a major plot point in the series and played a significant role in his actions and decisions.