The mysterious white clumps have been reported in over a hundred units of blood so far, most but not all in transfusion bags from a particular manufacturer. One desperately ill patient has died while receiving a transfusion of the adulterated blood (although officials hasten to say the patient was so ill that the association of the death with the transfusion may have been only coincidental) and there have been six other adverse reactions. NY Times Filters remove the clumps during transfusions, but what is causing them?