Fat embolism syndrome is a dire complication of long bone trauma. It is usually associated with neurological, hematological and respiratory involvement, the latter being the major cause of death. We present a case of severe fat embolism syndrome occurring 3 hours after a long bone injury, leading to permanent vegetative state and death without any respiratory signs. The diagnosis was confirmed by cytology of the bronchoalveolar lavage fluid. Clinical presentation of the puzzling fat embolism syndrome and diagnostic tests in suspected fat embolism syndrome are reviewed.