Deep Vein Thrombosis (DVT) with Pulmonary Embolism (PE): This is a common and serious condition where a blood clot forms in the deep veins of the legs and can break loose, traveling to the lungs, causing a pulmonary embolism. The symptoms of bilateral lower extremity swelling and chest pain are classic for this condition.

Heart Failure: This condition can cause fluid buildup in the body, leading to swelling in the legs and shortness of breath or chest pain due to the heart's inability to pump blood efficiently.
Pericarditis: Inflammation of the pericardium, the sac surrounding the heart, can cause chest pain and, if severe, can lead to fluid accumulation in the legs due to decreased cardiac output.
Nephrotic Syndrome: A condition characterized by excessive loss of protein in the urine, leading to low albumin levels, which can cause edema (swelling) in the legs and potentially chest pain if there are associated cardiac issues.

Pulmonary Hypertension: A condition where the blood pressure in the arteries of the lungs is too high, which can lead to right heart failure, causing leg swelling and chest pain. Missing this diagnosis can be fatal due to its progressive nature and impact on heart function.
Dissecting Aortic Aneurysm: A serious condition where there is a tear in the inner layer of the aorta, which can cause severe chest pain and, if the dissection extends to involve the renal or iliac arteries, can lead to leg swelling due to impaired blood flow.
Superior Vena Cava Syndrome: Obstruction of the superior vena cava can cause swelling in the upper body, including the legs if the obstruction is significant and affects venous return, and can also cause chest pain due to the increased pressure.

Lymphangiomatosis: A rare condition involving the lymphatic system that can cause swelling in the legs due to impaired lymphatic drainage and, in severe cases, can affect the chest, causing pain.
Ehlers-Danlos Syndrome with Vascular Complications: A genetic disorder that affects the body's connective tissue and can lead to vascular complications, including aneurysms or ruptures, which might present with chest pain and leg swelling due to vascular involvement.
Klippel-Trenaunay Syndrome: A rare congenital condition characterized by abnormal blood vessel formation, which can cause leg swelling and, in some cases, chest pain if there are associated cardiac anomalies or if the abnormal vessels lead to complications like thrombosis.