Differential Diagnosis for Lateral Base of Thumb Pain and Tenderness

Single Most Likely Diagnosis

• De Quervain's tenosynovitis: This condition is characterized by inflammation of the tendons on the lateral (thumb) side of the wrist, leading to pain and tenderness, especially when forming a fist, grasping, or turning the wrist. The location and nature of the pain make it the most likely diagnosis for lateral base of thumb pain.

Other Likely Diagnoses

• Scaphoid fracture: A common injury that can cause pain on the lateral side of the wrist, including the base of the thumb. The scaphoid bone is prone to fractures, especially with falls onto an outstretched hand.
• Thumb carpometacarpal (CMC) joint arthritis: Arthritis in the joint at the base of the thumb can cause pain and tenderness in the area, especially with gripping or twisting motions.
• Wrist ganglion cyst: A benign lump that can develop on the wrist, sometimes causing pain if it presses on nearby nerves or joints.

Do Not Miss Diagnoses

• Infectious tenosynovitis: Although less common, an infection within the tendon sheath can lead to severe consequences if not promptly treated, including permanent damage to the tendons and surrounding tissues.
• Gout or pseudogout: These conditions can cause sudden, severe pain and swelling in the joints, including those in the wrist and thumb, and require specific treatment to manage symptoms and prevent long-term damage.

Rare Diagnoses

• Giant cell tumor of the tendon sheath: A rare, benign tumor that can cause pain and swelling in the affected area.
• Nerve entrapment (e.g., superficial branch of the radial nerve): Compression or irritation of nerves in the wrist can cause pain, numbness, or tingling in specific areas, including the lateral base of the thumb.
• Kienböck's disease: A rare condition characterized by the collapse of the lunate bone in the wrist, which can cause pain on the lateral side of the wrist, among other symptoms.