Lymphedema: This condition is characterized by the abnormal accumulation of protein-rich fluid in the interstitial tissue, leading to swelling of one or more extremities. It can be primary (congenital) or secondary (acquired) due to surgery, infection, or trauma. The unilateral involvement of both an upper and a lower limb could suggest a secondary cause, such as surgical removal of lymph nodes or an infection affecting the lymphatic system.

Deep Vein Thrombosis (DVT): Although DVT typically presents with swelling of a single limb, in rare cases, it can cause swelling in multiple limbs if there are multiple clots or if the condition progresses to affect other veins. The swelling is usually accompanied by pain, warmth, and discoloration of the affected limb.
Chronic Venous Insufficiency: This condition results from the veins having problems returning blood from the legs back to the heart due to valve issues. It can lead to swelling, skin changes, and ulcers, typically in the lower limbs, but could potentially affect an upper limb if the condition is severe or if there's a significant obstruction in the venous return.
Infection or Cellulitis: Bacterial infections of the skin and soft tissues can cause localized swelling, redness, and warmth. While typically affecting one limb, in severe cases or with hematogenous spread, multiple limbs could be involved.

Superior Vena Cava Syndrome: Obstruction of the superior vena cava can lead to swelling of the upper body, including the arms, due to impaired venous return to the heart. This condition is life-threatening and requires immediate medical attention.
Tumor or Malignancy: Certain cancers can cause lymphedema or venous obstruction leading to limb swelling. For example, lymphoma can infiltrate lymph nodes and disrupt lymphatic drainage, while other tumors can compress or invade veins.
Pulmonary Embolism with Extensive DVT: Although less common, a large pulmonary embolism can lead to increased pressure in the venous system, potentially causing swelling in multiple limbs due to the body's attempt to compensate for the decreased cardiac output.

Klippel-Trenaunay Syndrome: A rare congenital condition characterized by port-wine stains, varicose veins, and bony and soft tissue hypertrophy, leading to limb swelling and enlargement.
Parkes Weber Syndrome: Similar to Klippel-Trenaunay, but with the addition of arteriovenous fistulas, which can cause increased blood flow to the affected limb, leading to swelling and hypertrophy.
Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and pain. It can sometimes affect the arms as well.