E! News reports that the fluffy feline passed away from a "cancer-like virus often associated with breeding," and that Kardashian, 32, had given the cat to sister Khloe's assistant, Sydney, after discovering she was allergic. (At the time, Sydney was grieving the loss of her own pet cat, who had passed away after 12 years.)
According to E!, Mercy's new owner decided to have her euthanized after learning that her kitten was terminally ill, and that "even aggressive treatment" wouldn't help her situation.
"Mercy was a gentle and loving kitten and we are all going to miss her so much," Kim wrote in a statement on her blog about the sad news. After explaining how she went to multiple allergists to try to find a cure for her cat allergy, and the details of the kitty's illness, she added: "Thanks to Sydney for making Mercy's short life one filled with love."