<prompt> Most common cause of thoracic aortic aneurysm isAtherosclerosisTuberculosisCystic degenerationSyphilitic  <response>: A AtherosclerosisDISEASES OF THE AORTA: ETIOLOGY ASSOCIATED FACTORSAortic aneurysmAortic occlusion Atherosclerosis Atherosclerosis Cystic medial necrosis Thromboembolism Tuberculosis Aortitis Syphilitic infection Syphilitic aortitis Mycotic infection Rheumatic aortitis Rheumatic aortitis Takayasus arteritis Trauma Giant cell arteritis Aortic dissection Cystic medial necrosis Systemic hypertension Atherosclerosis Takayasus arteritis Giant cell arteritis 