Protein C deficiency: Protein C is a protein in plasma that enters into the cascade of biochemical events leading to the formation of a clot. Deficiency of protein C results in thrombotic (clotting) disease and excess platelets with recurrent thrombophlebitis (inflammation of the vein that occurs when a clot forms). The clot can break loose and travel through the blood stream (thromboembolism) to the lungs causing a pulmonary embolism, brain causing a stroke (cerebrovascular accident), heart causing a heart attack, skin causing what in the newborn is called neonatal purpura fulminans, the adrenal gland causing hemorrhage with abdominal pain, abnormally low blood pressure (hypotension), and salt loss. Protein C deficiency is due to possession of one gene (heterozygosity) in chromosome band 2q13-14. The possession of two such genes (homozygosity) is usually lethal.