Evidence is presented to indicate that a profound thrombocytopenia and granulocytopenia occur during the second stage of the Shwartzman phenomenon, prior to the actual onset of hemorrhage in the prepared skin areas. These hematologic alterations appear to be due to accumulation of the cells mentioned in the capillary bed of the lungs and perhaps other internal organs. This seems to be consequent on certain changes in the platelets and polymorphonuclear leucocytes, which result in the formation of clumps of these elements.
In skin areas prepared for the Shwartzman phenomenon, the capillaries and small veins become occluded by masses of platelets and granulocytes after the intravenous challenging injection has been given. Following the interruption of blood supply necrosis of the involved vessels takes place, and hemorrhage occurs later where the vessel walls have lost their integrity.