Final answer:
The abrupt onset of symptoms and endoscopic findings suggest the patient has herpetic esophagitis, which is characterized by discrete ulcers in the esophagus.
Step-by-step explanation:
The patient presenting with abrupt-onset retrosternal pain and severe odynophagia (painful swallowing), accompanied by endoscopic findings of discrete ulcers with normal appearing surrounding mucosa, is likely suffering from herpetic esophagitis. This condition is typically caused by the herpes simplex virus and can cause acute symptoms in the upper gastrointestinal tract. While candidal esophagitis, reflux esophagitis, and cytomegalovirus (CMV) esophagitis can also present with esophageal ulcers, the sudden onset of symptoms and the appearance of discrete ulcers points more towards a herpetic etiology.