An 18-year-old male comes to your primary care clinic complaining of pain near the breastbone for the last three days. It is a sharp pain that gets worse when he presses on the bone, moves sideways, and when he takes a deep breath, coughs, or sneezes. He can’t even laugh comfortably. The pain has no relationship with meals. His grandmother gave him a nitroglycerin tablet, but it did not relieve the pain. He also took some over-the-counter antacids without any relief. On further questioning, he reveals that he has been doing lots of exercises as part of his athletic training, including lifting heavy weights in the gym to develop a “six-pack” physique. Vital signs: Temperature: 98.8 °F Heart rate: 67 beats/min Blood pressure: 110/78 mm Hg Respirations: 15 breaths/min Oxygen saturation: 98% on room air Physical examination: Significant for tenderness over the sternum and right-sided ribs. ECG: Normal. Laboratory tests: Normal troponin levels. What is the most likely diagnosis in this patient?
