Lymphedema: This condition involves the abnormal collection of protein-rich fluid in the interstitial tissue, leading to swelling. It can be primary (inherited) or secondary (acquired) due to surgery, infection, or trauma. Swelling often worsens throughout the day due to gravity and activity, which could explain improvement later in the day if the hand is elevated or less active.

Arthritis (Rheumatoid or Osteoarthritis): Morning stiffness and swelling are common in various forms of arthritis. While symptoms can fluctuate, they might seem to improve as the day progresses due to increased movement and warmth.
Overuse or Repetitive Strain Injury: Activities that involve repetitive motions of the hand can lead to swelling, which may decrease with rest later in the day.
Cellulitis: A bacterial skin infection that can cause swelling, redness, and warmth. While it typically worsens without treatment, early stages or mild cases might seem to fluctuate in severity.

Deep Vein Thrombosis (DVT): Although DVTs are more commonly associated with the legs, they can occur in the arms. Swelling that improves with elevation could be a sign, but it's crucial to consider other symptoms like pain and warmth.
Compartment Syndrome: A serious condition resulting from increased pressure within a muscle compartment, which can lead to nerve and muscle damage. It typically presents with severe pain, but early stages might be missed if not carefully evaluated.
Infection (Abscess or Septic Arthritis): Any infection in the hand can cause swelling. While these conditions are usually painful and worsen over time, early detection is critical to prevent serious complications.

Sarcoidosis: A condition that can cause inflammation in various parts of the body, including the skin, leading to swelling. It's less common but should be considered in the differential diagnosis of unexplained swelling.
Venous Insufficiency: Similar to lymphedema, but due to problems with venous return. It's more common in the legs but can occur in the arms, leading to swelling that might improve with elevation.
Klippel-Trenaunay Syndrome: A rare congenital condition characterized by abnormal development of blood vessels, leading to swelling and other symptoms. It's typically identified at birth or in early childhood but could be considered in cases of unexplained limb swelling.