The differential diagnosis of two cases of chronic periaortitis.

The imaging features of chronic periaortitis resemble those of infected aneurysms. Two illustrative cases of chronic periaortitis, in which the etiologies were caused by IgG4-related disease, are presented. The first case involved a 68-year-old man who presented with vague discomfort in his lower abdomen. The second case was a 42-year-old man who presented with a fever of 38°C and persistent, vague chest discomfort. Both cases demonstrated an increased amount of connective tissue around the aorta in computed tomography images and low intensity in the T2-weighed sequence and high intensity in the diffusion-weighed sequence, suggesting the presence of inflammation, in the magnetic resonance imaging. Negative blood cultures, elevated IgG4 levels, and pathological findings confirmed the diagnosis as chronic periaortitis due to IgG4-related disease. This is a newly recognized syndrome of unknown etiology, characterized by a fibroinflammatory condition, tumefactive lesions, and a dense lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells. Both cases were successfully treated with corticosteroids. Infected aneurysms need to be carefully differentiated from this syndrome in view of the similar imaging features.