Purpura fulminans. A cutaneous manifestation of severe protein C deficiency.

Protein C, when activated, is a vitamin K-dependent serine protease that has anticoagulant and profibrinolytic activities. An increased risk of thrombotic disease is associated with deficiency of this enzyme. A neonate developing purpura fulminans with internal thrombotic complications and congenital absence of protein C is described. Family studies showed partial protein C deficiency in the subject's symptom-free parents and two of three siblings. Clinically and histopathologically similar lesions are also seen in two acquired conditions in which there is a thrombotic tendency: coumarin necrosis and purpura fulminans of childhood, both of which are probably the result of transient protein C deficiency. We conclude that purpura fulminans can represent a cutaneous marker of acquired or congenital protein C deficiency.