Differential Diagnosis

• Single most likely diagnosis
  • Musculoskeletal strain: The patient's symptoms of tenderness to palpation of paraspinal muscles and intercostal muscles/latissimus dorsi, pain on lateral bending, and recent physical activity (mowing on a riding lawn mower) are consistent with a musculoskeletal strain. The patient's age and presence of low back pain on the same side also support this diagnosis, as older adults are more prone to musculoskeletal injuries.
• Other Likely diagnoses
  • Thoracic outlet syndrome: The patient's symptoms of pain and tenderness in the mid-back and intercostal muscles, as well as pain on lateral bending, could be consistent with thoracic outlet syndrome. However, this diagnosis is less likely given the absence of symptoms such as numbness, tingling, or weakness in the arm.
  • Rib fracture or costochondritis: The patient's symptoms of pain and tenderness in the intercostal muscles and latissimus dorsi could be consistent with a rib fracture or costochondritis, particularly given the recent physical activity. However, these diagnoses are less likely given the absence of a reported trauma or fall.
  • Myofascial pain syndrome: The patient's symptoms of tenderness to palpation and pain on movement could be consistent with myofascial pain syndrome, particularly given the presence of low back pain on the same side.
• Do Not Miss diagnoses
  • Pulmonary embolism: Although less likely, pulmonary embolism is a potentially life-threatening condition that can present with sudden onset of chest or back pain, particularly in older adults. The patient's recent physical activity and age increase the risk of pulmonary embolism.
  • Aortic dissection: Aortic dissection is a rare but potentially life-threatening condition that can present with sudden onset of severe back or chest pain, particularly in older adults with a history of hypertension. The patient's age and symptoms of back pain warrant consideration of this diagnosis.
• Rare diagnoses
  • Osteoporotic compression fracture: Although less likely, osteoporotic compression fracture is a possible diagnosis in older adults with back pain, particularly if they have a history of osteoporosis or recent trauma.
  • Spinal tumor or metastasis: Spinal tumor or metastasis is a rare but possible diagnosis in older adults with back pain, particularly if they have a history of cancer or unexplained weight loss.