Inflammatory abdominal aortic aneurysms: a disease entity? Histological analysis of 60 cases of inflammatory aortic aneurysms of unknown aetiology.

Sixty inflammatory aortic aneurysms of unknown aetiology were examined by serial sections. The histological findings failed to reveal significant differences in either thoracic or abdominal aneurysms with or without marked adventitial fibrosis. Their identical morphology does not favour the existence of a special disease entity of so-called inflammatory abdominal aortic aneurysms (IAAA). Absence or existence of giant cells of any type, occurrence of plasma cells, eosinophils, granulomas, fibrinoid necrosis and adventitial fibrotic thickening cannot be considered as variables which help in differentiation. IAAA are characterized by a marked predominance of male patients and a rather benign clinical course. They usually affect the age group around 60 years. They are not rare and do not seem to be restricted to certain races. Their aetiology, like that of the cases affecting the thoracic aorta (Takayasu's disease, non-specific aortitis) remains unknown, although autoimmune diseases, the retroperitoneal fibrosis of Ormond and arteriosclerosis may be related. However, on the basis of the present evidence we cannot consider them to be one of these diseases. There are no morphological findings which would justify the separation of IAAA from Takaysu's disease.