Repetitive Strain Injury (RSI): The patient's symptoms are consistent with RSI, which is a common condition caused by repetitive movements or overuse of the thumbs, often seen in individuals who use their hands for work or hobbies. The fact that the pain is worse on the non-dominant hand may suggest that the patient is using this hand more than usual for certain activities.

Osteoarthritis: A common condition that can cause thumb pain, especially in women. The pain can be bilateral and may be worse on the non-dominant hand if the patient is using this hand more for certain activities.
De Quervain's Tenosynovitis: A condition that affects the tendons on the thumb side of the wrist, causing pain and tenderness, especially when forming a fist or grasping objects.
Trigger Thumb: A condition that causes the thumb to catch or lock when extended, often due to inflammation of the tendon sheath.

Gout: Although less common in women, gout can cause sudden, severe pain and swelling in the thumbs. It's essential to consider this diagnosis to avoid missing a potentially treatable condition.
Infection (e.g., Septic Arthritis): Infection in the thumb joint can cause severe pain, redness, and swelling. Early diagnosis and treatment are crucial to prevent long-term damage.
Tumor (e.g., Giant Cell Tumor): Although rare, tumors can cause thumb pain and should be considered in the differential diagnosis to avoid missing a potentially serious condition.

Scleroderma: A rare autoimmune disorder that can cause thickening of the skin and connective tissue, leading to limited mobility and pain in the thumbs.
Ehlers-Danlos Syndrome: A rare genetic disorder that affects the connective tissue, causing joint hypermobility and pain, including in the thumbs.
Psoriatic Arthritis: A rare condition that causes inflammation and pain in the joints, including the thumbs, often associated with psoriasis.