The term periarteritis nodosa was given by Kussmaul and Maier,1 in 1866, to a distinct pathologic entity characterized by the presence of nodular thickenings of various sizes in the walls of small and medium size blood vessels and caused by inflammatory disease. The disease is not rare. About 120 cases have been reported and the various aspects of the condition fully elucidated in this country by Longcope,2 Klotz3 and Ophüls ;4 and abroad, rather voluminously, by Gruber.5
While the lesion which Kussmaul and Maier described has remained established as a separate entity, it has become apparent through study of successive cases that it is in reality an arteritis or panarteritis involving, as it usually does, all the layers of the wall of the artery. Further, it is clear that macroscopic nodes are entirely absent in some cases. The lesion is then found to affect only