Cancergate round 2? In an exclusive sneak peek of Season 6 of The Real Housewives of Beverly Hills, Lisa Vanderpump questions Yolanda Foster’s Lyme disease.

“I don’t quite understand what’s wrong with her,” Vanderpump tells the camera after discussing Foster’s illness with castmate Kyle Richards. “I don’t know if it is Lyme disease, but I’m not criticizing her. I’m just questioning it.”

As fans are well aware, Foster has been battling the bacterial infection, which can cause autoimmune responses, for years.

“She was having some anesthetic, she had a stem cell transplant — just a lot of stuff,” a confused Vanderpump explains to Richards over lunch in the clip.

Foster, who had to sit out of most of the Season 5 reunion special due to her health, explains to the camera in the sneak peek that she was diagnosed with neurological Lyme disease in 2012. “You know it’s been a journey. I look quite normal, but yet I’m so sick,” she explains. “I have weakness in my legs, no brain function — I mean, I haven’t driven a car in three years.”

After detailing all of the different treatments she’s explored all over the world, a frustrated Foster concludes, “Its been like trying to uncover a murder mystery.”

During an interview with Entertainment Tonight, Richards revealed that some of her fellow costars are also questioning how sick Foster is. The former supermodel has revealed that two of her kids, Bella and Anwar Hadid, also suffer from the disease.

Watch the clip above. Season 6 of The Real Housewives of Beverly Hills premieres Dec. 1 at 9 p.m. ET on Bravo.