Activation of the kallikrein-kinin system in Rocky Mountain spotted fever.

Activation of the kallikrein-kinin system, as indicated by increased plasma kallikrein and depleted plasma kininogen, prekallikrein, and kallikrein inhibitor, was observed in five patients with Rocky Mountain spotted fever. Four of the patients had petechial rashes characteristic of vasculitis. Three patients had alterations in coagulation consistent with disseminated intravascular coagulation, although no hemorrhagic syndrome was found. Our data, along with the known physiologic actions of kinins, suggest a possible role for the kallikrein-kinin system in the pathophysiology of vasculitis, disseminated intravascular coagulation, circulatory shock, and other complications of infection with Rickettsia rickettsii.