Review Question - QID 214185

A 46-year-old man presents to his primary care physician with a 3-day history of dark stools and shortness of breath. He reports a 3-month history of epigastric pain that occurs 1-3 hours after eating and is worse with spicy foods. He has a decreased appetite and has lost 5 lbs. He smoked 1 pack per day for 5 years but recently quit. He was in the Dominican Republic 6 months ago to visit family but denies any other travel or sick contacts. He has a history of tension headaches and irritable bowel syndrome. His medications include ibuprofen and probiotics. His temperature is 97.9°F (36.6°C), blood pressure is 100/65 mmHg, pulse is 90/min, and respirations are 18/min. On physical exam, there is conjunctival pallor. His abdomen is tender to palpation in the epigastric area with no rebound or guarding. The remainder of the exam is unremarkable. Preliminary lab results are as follows:

Hemoglobin: 7.2 g/dL
Platelets: 176,000/mm^3
Heme occult stool test: Positive

Leukocyte count and differential:
Leukocyte count: 11,000/mm^3
Segmented neutrophils: 56%
Bands: 2%
Eosinophils: 1%
Basophils: 0.8%
Lymphocytes: 35%
Monocytes: 5%

Upper endoscopy shows diffuse reddening of the gastric mucosa and a 1 cm lesion with a smooth and flat base located in the first part of the duodenum. Which of the following most likely contributed to the findings on endoscopy?