Brazilian butt lift refers to augmentation of the buttocks with fat transfer. It is currently quite a popular procedure but it does not come without risks. There have been a number of deaths reported in the literature and I believe that it has an unacceptable mortality rate for what is essentially a cosmetic procedure.
The most common cause of death is from a fat embolism which may result in a pulmonary embolism or blockage of the pulmonary artery. Fat emboli are similar to clots breaking off from a deep vein thrombosis.