It is recommended to speak exclusively of IA when a disease process is involved which is caused by the entry of anthrax bacilli from the air passages, and not of pulmonary anthrax, since the lungs are affected only in part of the cases. In cases diagnosed as IA, there are hemorrhagic or hemorrhagic-necrotic foci in the trachea, variable in size and at times reaching down to a cartilaginous ring, with apparent preference for the bifurcation and the neighboring sector of the main bronchi. Suitable microscopic preparations reveal the invasion of anthrax bacilli between the epithelia of the tracheo- bronchial mucosa, sloughing of epithelia and formation of mucosal erosion whose region is occupied by anthrax bacilli mixed with leukocytes. Pulmonary foci of anthrax may be formed by aspiration of free anthrax bacilli into the deeper airways, as far as the alveoli, without lymphogenic dissemination of bacilli. Even processes limited to the tracheo-bronchial mucosa usually cause pronounced hemorrhagic swelling of the regional lymph nodes, the mediastinal, hilus and bifurcation lymph nodes, as well as accumulation of variable amounts of serous- hemorrhagic effusions in the pleural spaces. The resultant clinical signs are identical with those of pure pulmonary anthrax, consisting of high-grade cyanosis, strongly accelerated and diminished pulse, pronounced feebleness, occasional high temperature. The prognosis of IA, even upon recognition, is extremely poor.
Trans. of Virchow's Archiv fuer Pathologische Anatomie und Physiologie und Klinische Medizin (Germany) v254 p363-378 1925.