Thane: You don't have to worry about the rest of the crew. My illness is not communicable, even to other drell. / Thane: It's called Kepral's Syndrome.
There is a deeper reason he is offering his services. Go to the life support chamber on deck 3 so Shepard can discuss Thane’s reasons for joining the crew, Much of it has to do with his own condition; he is dying from Kepral’s Syndrome but expects to live as long as the mission needs. It will be a good final assignment for him.
Attending Doctor: The doctors were able to repair a lot of the trauma. However, mister... um, Krios is in the final stages of Kepral's Syndrome. / Attending Doctor: At its worst, Kepral's Syndrome intereferes with his blood's ability to carry oxygen. And he lost a lot.
2013 March 5, “LOVABLE VARREN GOES FROM HOME TO HOME, CHANGING LIVES”, in BioWare Blog[2] (Blog), archived from the original on 07 March 2013[3]:
He has lived on Tuchanka, on Illium, and on the Citadel. He has battled in pit fights, assisted as a therapy animal for drell children with early-stage Kepral’s Sydrome[sic – meaning Kepral's Syndrome], and was even, for a brief period of time, co-chair of Elkoss Combine. His current show-breed name is Prince Grimrender of Gembat, and in an investigative report, we explore the lives this lovable varren has touched–and changed.
Only the drell got Kepral's Syndrome. They were a strong species, but their lungs were their weakness.[…]Any moisture in the air was a slow poisonous rot filling them up until they finally stopped breathing. It was called Kepral's Syndrome, and Anax's parents had died of it when she was six.
2021 February 3, Cian Maher, quoting Chris Hepler, “Mass Effect 3 Writers Toyed With The Idea Of Curing Thane, But A Codex Entry Made It Very Difficult”, in TheGamer[5], archived from the original on 03 February 2021[6]:
“We kicked around ideas for a cure for Thane in early concepting, but Kepral's Syndrome was described in Mass Effect 2 as really, really, bogusly incurable,” Thane writer Chris Hepler explains. “The only ones with tech that might cure him would be the Reapers, and so we had some rough ideas that maybe Cerberus or someone would try to lure Shep into a trap with the promise of a cure. But it never panned out. “So Mac Walters and I eventually concluded that Thane wasn't going to make it. Shepard could kill just about anything that walks, but ultimately, Thane would serve as a reminder that you can't beat mortality itself. The issue got slightly muddied because of Kai Leng stabbing him, but it's a combination of his wound and Kepral's Syndrome that kills him – all the medi-gel in the world can't clear his lungs.”
