Cervical Radiculopathy: This condition involves nerve root compression in the cervical spine, which can cause pain and symptoms in the neck, shoulder, and arm, including carpal tunnel symptoms, medial and lateral epicondyle pain due to referred pain patterns. The one-sided nature of the symptoms supports this diagnosis.

Thoracic Outlet Syndrome (TOS): TOS can cause neck and shoulder pain and can also lead to symptoms in the arm and hand, including carpal tunnel-like symptoms, due to compression of the nerves and/or blood vessels that pass through the thoracic outlet.
Repetitive Strain Injury: This is a broad category of injuries that can occur from repetitive motion and can affect multiple areas, including the neck, shoulder, elbow, and wrist, leading to a variety of symptoms including those described.
Cubital Tunnel Syndrome: While primarily causing symptoms in the ulnar distribution of the hand, cubital tunnel syndrome can sometimes present with pain radiating up to the elbow and, less commonly, to the shoulder or neck, especially if there is a component of repetitive strain or poor posture.

Pancoast Tumor: A type of lung cancer located at the top of the lung, which can cause shoulder and arm pain due to invasion of the brachial plexus. Although rare, missing this diagnosis could be catastrophic.
Multiple Myeloma or Other Bone Cancers: These conditions can cause bone pain, including in the areas described, and are critical not to miss due to their serious nature and potential for treatment if caught early.
Stroke or Transient Ischemic Attack (TIA): While less likely to present with the exact combination of symptoms described, any sudden onset of neurological symptoms, including pain, should prompt consideration of vascular events, especially in patients with risk factors.

Amyotrophic Lateral Sclerosis (ALS): A progressive neurological disease that affects nerve cells in the brain and spinal cord, leading to loss of muscle control. Early symptoms can sometimes be mistaken for more common conditions like carpal tunnel syndrome or cervical radiculopathy.
Brachial Plexitis (Neuralgic Amyotrophy): An inflammatory condition of the brachial plexus that can cause severe pain in the shoulder and arm, followed by weakness and atrophy of the affected muscles. It is relatively rare and can be overlooked in the differential diagnosis of arm pain.