Differential Diagnosis for Natalie's Shoulder Pain

Single Most Likely Diagnosis

• Musculoskeletal Strain: This is the most likely diagnosis given the sharp, constant pain in the back of Natalie's shoulder. Musculoskeletal strains are common and can occur due to overuse, poor posture, or direct injury to the muscles or tendons in the shoulder area.

Other Likely Diagnoses

• Tendinitis: Inflammation of the tendons in the shoulder, such as the rotator cuff, could cause sharp pain, especially with movement.
• Bursitis: Inflammation of the bursae, fluid-filled sacs that cushion bones, tendons, and muscles near joints, could also lead to pain in the shoulder area.
• Referred Pain from the Neck: Sometimes, pain from the cervical spine can refer to the shoulder area, suggesting a possible cervical spine issue.

Do Not Miss Diagnoses

• Myocardial Infarction (MI): Although less common, it's crucial not to miss cardiac causes of shoulder pain, as MI can sometimes present with referred pain in the shoulder or arm.
• Pulmonary Embolism: Similar to MI, a pulmonary embolism can cause sudden, severe pain that might be referred to the shoulder area, especially if it involves the upper lobes of the lungs.
• Gallbladder Disease: Gallbladder inflammation or stones can cause right shoulder pain due to referred pain from the phrenic nerve.

Rare Diagnoses

• Pancoast Tumor: A rare type of lung cancer located at the top of the lung that can cause shoulder pain due to local invasion of the brachial plexus or ribs.
• Thoracic Outlet Syndrome: Compression of the nerves or blood vessels that pass into the thoracic outlet (the space between your collarbone and first rib) can cause pain in the shoulders and neck.
• Polymyalgia Rheumatica: An inflammatory disorder that causes muscle pain and stiffness, typically in the shoulders and hips, though it's more common in older adults.