TTP (Thrombotic thrombocytopenic purpura)

Ok, so my dad was diagnosed w/ stage 3 Adenocarcinoma Lung Cancer in Oct. Through treatments they were abled to shrink his tumors 60%. But now he is suffering from TTP. At first the DR said it was from the Chemo and will leave his system in 2 weeks. That was 6 weeks ago and now he has been in ICU for over a week and his Hemoglobin is at 7 and they have no awnsers as to where all his Red Cells are going. They have sent him to another hospital because they cannot figure this out. I'm scared my dad will not make it out of the hospital. Has anyone had or seen a case of TTP  this severe and if so do you have any suggestions as to what I can ask the DR to check for or try. At this point he is getting several blood transfusions a day and going through Plasma Exchange everyday. Anyone that can shed any light on this will have my gratitude as I feel him slipping away and desperatly want to save him!!!