There have been a number of cases of sclerosis of the pulmonary arteries, either alone, or associated with general systemic arteriosclerosis.
A primary and a secondary form are recognized, the former in conjunction with congenital malformations of the heart, the latter as the result of severe infection or of mitral stenosis. These two causes seem to be the most important in the production of the arterial changes. The cases thus far described have revealed widespread thickening of the pulmonary arteries. If one may judge by the description of the pathologic changes, the condition is quite similar to that produced in a vein by transplantation along the course of an artery. The diffuse form with connective tissue thickening of all coats has been generally described. There is also obliterating endarteritis of the smaller vessels. In the etiology of the condition severe infection seems to play a prominent rôle. The constant presence of right ventricular hypertrophy is interesting, the heart dullness extends, as a rule, far to the right of the sternum. In some of the cases no demonstrable changes were observed in the bronchial arteries or in the pulmonary veins.
Sanders has described a case of primary pulmonary arteriosclerosis with hypertrophy of the right ventricle.
Recently Warthin[2] has reported a case of syphilitic sclerosis of the pulmonary artery which places the lesion in exactly the same category as that of syphilis in the systemic arteries. There was also aneurysm of the left upper division present and, to settle the etiologic nature of the process, Spirochete pallida were found in the wall of the aneurysm sac and in that of the pulmonary artery. The microscopic picture in the pulmonary artery could not be told from that in a syphilitic aorta.
Sclerosis of the Veins
Phlebosclerosis not infrequently occurs with arteriosclerosis. It is seen in those cases characterized by high blood pressure. Such increased pressure in the veins is due, for example, to cirrhosis of the liver which affects the portal circulation, or to mitral stenosis which affects the pulmonary veins. The affected vessels are usually dilated. The intima shows compensatory thickening especially where the media is thinned. As a rule all the coats are involved in the connective tissue thickening. Occasionally hyaline degeneration or calcification of the new-formed tissue is seen. "Without existing arteriosclerosis the peripheral veins may be sclerotic usually in conditions of debility, but not infrequently in young persons." (Osler.)
In many cases of arteriosclerosis, the pathologic changes are not confined to the arteries, but are found in the veins as well as in the capillaries. Such cases could be called angiosclerosis.