patient thomas cox and his wife lori. t first glance, thomas seems fine-- but he's not. >> thomas cox: i've got f.t.d. >> dr. miller: okay, and has that affected you so far? >> thomas cox: no. >> whitaker: in fact, lori cox says that, starting a few years ago, thomas lost interest in her, in their son, and in his work-- so much that he was fired from his job. by now, he's pretty much reduced to looking at photos on his phone. >> thomas cox: that's bugatti. >> lori cox: that's our dog. ( laughs ) >> dr. miller: ah. your dog. >> lori cox: i can blame the disease. i can say that the disease stole my-- my husband. >> dr. miller: yes. when a family sees someone with this illness, they don't recognize them. this is not the person i married, that i love. this is not my father, or my mother. >> whitaker: you have said that f.t.d. attacks people at the very soul of their humanity. >> dr. miller: this is profound as anything that can happen to a human being. it robs us of our very essence of our humanity, of who we are. >> whitaker: