Atherosclerosis: This is the most common cause of subclavian artery stenosis, particularly in older adults, due to the buildup of plaque in the arterial walls, leading to narrowing and reduced blood flow.

Takayasu Arteritis: A large vessel vasculitis that can cause stenosis or occlusion of the subclavian artery, more commonly seen in younger women.
Fibromuscular Dysplasia: A non-atherosclerotic, non-inflammatory vascular disease that affects medium- and large-sized arteries, including the subclavian artery, leading to stenosis.
Radiation Arteriopathy: Stenosis or occlusion of the subclavian artery can occur as a late complication of radiation therapy, particularly in patients who have received radiation to the chest or neck.

Subclavian Steal Syndrome: A condition where stenosis or occlusion of the subclavian artery leads to reversal of blood flow in the vertebral artery, which can cause neurological symptoms such as syncope, vertigo, and arm weakness. Missing this diagnosis could lead to significant morbidity.
Aortic Dissection: Although less common, aortic dissection can extend to involve the subclavian artery, leading to stenosis or occlusion. This is a medical emergency that requires prompt diagnosis and treatment.
Giant Cell Arteritis: A large vessel vasculitis that can involve the subclavian artery, leading to stenosis. Missing this diagnosis could lead to vision loss or other serious complications if not treated promptly.

Thromboangiitis Obliterans (Buerger's Disease): A rare disease of the blood vessels that can cause stenosis or occlusion of the subclavian artery, typically seen in young smokers.
Arterial Thoracic Outlet Syndrome: Compression of the subclavian artery by the thoracic outlet can lead to stenosis, although this is a less common cause.
Vasculitis due to other rare conditions (e.g., Kawasaki disease, polyarteritis nodosa): These conditions can also cause subclavian artery stenosis, although they are much less common than the other diagnoses listed.