Cellulitis: This is a common bacterial skin infection that can cause swelling, redness, and warmth of the affected leg. It's often accompanied by fever and pain.

Deep Vein Thrombosis (DVT): A blood clot in the deep veins of the leg can cause swelling, pain, and discoloration. Risk factors include recent surgery, immobility, and cancer.
Lymphedema: This condition is characterized by the abnormal collection of protein-rich fluid in the interstitial tissue, leading to swelling of the leg. It can be primary (inherited) or secondary (due to surgery, infection, or trauma).
Chronic Venous Insufficiency: This condition occurs when the veins have problems returning blood from the legs to the heart, leading to swelling, varicose veins, and skin changes.

Compartment Syndrome: A medical emergency where increased pressure within a muscle compartment leads to inadequate blood supply, causing severe pain, swelling, and potentially permanent damage if not promptly treated.
Necrotizing Fasciitis: A life-threatening infection that destroys the tissue under the skin, including fat and the tissue covering the muscles (fascia). It requires immediate medical attention.
Pulmonary Embolism (if DVT is suspected): A blood clot that breaks loose and travels to the lungs can be fatal. Symptoms may include sudden onset of shortness of breath, chest pain, and cough.

Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and pain. It's often mistaken for lymphedema.
Fabry Disease: A rare genetic disorder that can cause swelling in the legs due to the accumulation of a particular type of fat in the body's cells.
Klippel-Trenaunay Syndrome: A rare congenital condition characterized by abnormal blood vessel formation, leading to swelling, varicose veins, and skin discoloration in the affected leg.