Peptic Ulcer Disease (PUD): This is the most common cause of stomach ulcers, often related to Helicobacter pylori infection or the use of nonsteroidal anti-inflammatory drugs (NSAIDs). The symptoms and presentation typically align with PUD, making it the first consideration.

Gastritis: Inflammation of the stomach lining can sometimes present similarly to ulcers and may be caused by similar factors, including H. pylori infection or NSAID use.
Gastroesophageal Reflux Disease (GERD): While primarily causing esophageal symptoms, severe GERD can lead to stomach inflammation and potentially ulcers.
Zollinger-Ellison Syndrome: A rare condition characterized by excessive gastric acid production due to a gastrinoma, leading to severe peptic ulcers.

Malignancy (Gastric Cancer): Although less common, gastric cancer can present with ulcer-like symptoms. Missing this diagnosis could be fatal, making it crucial to consider, especially in older patients or those with risk factors.
Ingestion of Caustic Substances: Accidental or intentional ingestion of corrosive substances can cause severe stomach ulcers and perforation, requiring immediate medical attention.
Vascular Disorders (e.g., Dieulafoy's Lesion): A rare cause of gastrointestinal bleeding, which can mimic the presentation of a stomach ulcer.

Crohn's Disease: Although more commonly associated with the small intestine and colon, Crohn's disease can affect any part of the gastrointestinal tract, including the stomach, and cause ulcers.
Sarcoidosis: A systemic disease that can rarely cause stomach ulcers among its myriad manifestations.
Behçet's Disease: A form of vasculitis that can cause ulcers throughout the gastrointestinal tract, including the stomach, though it is more commonly associated with oral and genital ulcers.