Review Question - QID 214455

A 42-year-old woman presents to the emergency department with complaints of fever and cough. She reports symptom onset about 2 days ago, and the cough has been progressively getting worse. The patient endorses rust-colored sputum, dyspnea, and overall malaise. Her past medical history is significant for rheumatoid arthritis for which she is taking infliximab and methotrexate, 2 episodes of bacterial pneumonia within the past 6 months, and multiple episodes of cellulitis. Her family history is significant for rheumatoid arthritis in her mother. A physical examination demonstrates decreased breath sounds at the left lower lobe and a palpable left upper quadrant (LUQ) abdominal mass. There is also notable ulnar deviation of the 3rd and 4th digits of the hand bilaterally. Laboratory studies are shown below.

Hemoglobin: 13.6g/dL
Hematocrit: 38%
Leukocyte count and differential:
Leukocyte count: 3,102/mm^3
Segmented neutrophils: 41%
Bands: 5%
Eosinophils: 3%
Basophils: 0.7%
Lymphocytes: 42%
Monocytes: 8%
Platelet count: 230,000/mm^3

What is the most likely explanation for this patient’s symptoms?