A 66-year-old man comes to the office for a routine visit. He has a history of hypertension and osteoarthritis. The patient has smoked a pack of cigarettes daily for 40 years and occasionally drinks 1 or 2 glasses of wine but does not use illicit drugs. Blood pressure is 142/82 mm Hg and pulse is 80/min. Cardiopulmonary examination is normal. There is a pulsating, central abdominal mass on physical examination. Which of the following pathologic conditions is the most likely underlying cause of this patient's abnormal findings?

Question

A 66-year-old man comes to the office for a routine visit.  He has a history of hypertension and osteoarthritis.  The patient has smoked a pack of cigarettes daily for 40 years and occasionally drinks 1 or 2 glasses of wine but does not use illicit drugs.  Blood pressure is 142/82 mm Hg and pulse is 80/min.  Cardiopulmonary examination is normal.  There is a pulsating, central abdominal mass on physical examination.  Which of the following pathologic conditions is the most likely underlying cause of this patient's abnormal findings?

Quizplus · Accepted Answer

This patient's pulsating, central abdominal mass most likely represents an abdominal aortic aneurysm (AAA), which is a focal dilation of the abdominal aorta that typically occurs below the renal arteries. AAA is associated with several risk factors (eg, age >60, smoking, hypertension, male sex, family history) that lead to oxidative stress, vascular smooth muscle apoptosis, and chronic transmural inflammation of the aorta. Inflammatory cells (particularly macrophages) release matrix metalloproteinases and elastases that degrade extracellular matrix components (eg, elastin, collagen), leading to weakening and progressive expansion of the aortic wall. Furthermore, ischemia of the tunica media may play a role as the infrarenal abdominal aorta has a tenuous vasa vasorum, and atherosclerotic thickening of the intimal layer increases the diffusion distance for oxygen. (Choice B) Cystic medial necrosis is characterized by loss of smooth muscle, collagen, and elastic tissue with formation of cystic mucoid spaces in the aortic media. Patients with Marfan syndrome develop cystic medial degeneration of the aortic root at a young age, predisposing them to ascending aortic aneurysm and dissection. (Choice C) An intimal tear in the aortic wall is the primary event involved in the pathophysiology of aortic dissection. Patients typically present with tearing chest pain that radiates to the back. Proximal dissections involving the ascending aorta can cause unequal blood pressure in the arms, aortic valve regurgitation (eg, diastolic decrescendo murmur at the right sternal border), and cardiac tamponade. (Choice D) Malignant endothelial proliferation is characteristic of angiosarcoma, a neoplasm that arises from blood or lymphatic vessels in the subcutaneous tissue and most frequently affects the scalp and face. (Choice E) Microbial infection (usually bacterial) can cause localized dilation of an artery due to destruction of the vessel wall. Trauma, bacteremic seeding, or septic emboli (mycotic aneurysm) can cause infected aneurysms, which typically present with painful, pulsatile masses and systemic signs such as fever and malaise. (Choice F) Vasa vasorum endarteritis ("endarteritis obliterans") in the thoracic aorta is thought to be the mechanism by which syphilis causes thoracic aortic aneurysm. Educational objective: Abdominal aortic aneurysm is associated with risk factors (eg, age >60, smoking, hypertension, male sex, family history) that lead to chronic transmural inflammation and extracellular matrix degradation within the wall of the aorta. This leads to weakening and progressive expansion of the aortic wall, resulting in aneurysm formation, typically below the renal arteries. __________ References: Understanding the pathogenesis of abdominal aortic aneurysms. (http://www.ncbi.nlm.nih.gov/pubmed/26308600)

A 66-Year-Old Man Comes to the Office for a Routine