Differential Diagnosis for 32-year-old Female with Sudden Onset Shoulder Pain

Single Most Likely Diagnosis

• Subscapular Bursitis or Rotator Cuff Tendinitis: The patient's symptoms of sudden onset shoulder pain after an unusual activity, pain with extension and overhead reaching, and hypersensitivity to touch are consistent with an inflammatory condition such as subscapular bursitis or rotator cuff tendinitis. The improvement with a Medrol dose pack further supports this diagnosis.

Other Likely Diagnoses

• Golfer's Elbow (Medial Epicondylitis): Although the patient is a right-handed person using an opposite grip, the pain with straightening the elbow and the need to shrug the shoulder to reduce pain could suggest a referral pain pattern or associated condition like golfer's elbow.
• Thoracic Outlet Syndrome: The patient's symptoms of pain with arm extension and overhead activities could be related to thoracic outlet syndrome, especially if there is compression of the nerves or vessels in the thoracic outlet.
• Adhesive Capsulitis (Frozen Shoulder): Although the range of motion is currently normal, the patient's pain pattern and the fact that she can only straighten her elbow if her shoulder is shrugged could be early signs of adhesive capsulitis.

Do Not Miss Diagnoses

• Cervical Radiculopathy: Despite the relatively unremarkable cervical MRI, it's crucial to consider cervical radiculopathy, especially if there are any symptoms suggestive of nerve root compression, as this condition can have serious implications if missed.
• Infection or Septic Arthritis: Although less likely given the lack of systemic symptoms and the improvement with steroids, infection or septic arthritis must be considered, especially if the patient's condition worsens or does not improve with treatment.
• Tumor: A tumor could cause shoulder pain and must be considered, especially if the pain is persistent and unexplained by other diagnoses.

Rare Diagnoses

• Quadrilateral Space Syndrome: This is a rare condition that involves compression of the axillary nerve and/or posterior circumflex humeral artery, which could cause shoulder pain and weakness.
• Suprascapular Neuropathy: This condition involves compression of the suprascapular nerve and could cause shoulder pain and weakness, particularly with activities involving arm elevation.
• Scapulothoracic Bursitis: Inflammation of the bursae between the scapula and thoracic wall could cause pain with movements of the shoulder and arm.