Review Question - QID 212637

A 46-year-old woman presents to the emergency department with progressive dyspnea and chest pain. She reports that her symptoms started 1 week ago and have gotten progressively worse. The chest pain is left-sided and is exacerbated by coughing or deep breaths. She also endorses a 6-month history of joint pains involving her knees, elbows, and digits. She does not have a significant medical or surgical history. She takes ibuprofen as needed. She works as a pre-school teacher. The patient’s temperature is 99°F (37.2°C), blood pressure is 120/78 mmHg, pulse is 89/min, and respirations are 17/min with an oxygen saturation of 93% on room air. On physical examination, a friction rub upon inspiration/expiration and crackles are appreciated at the base of the left lung. She has an erythematous rash that spans the bilateral cheeks and nose. There are also scattered ecchymoses on her arms and legs. A chest radiograph shows a small left-sided pleural effusion. A complete blood count is obtained, as shown below:

Hemoglobin: 9 g/dL
Hematocrit: 28%
Leukocyte count: 1,500/mm^3 with normal differential
Platelet count: 80,000/mm^3

A urinalysis shows elevated protein levels. Serologic antibodies are pending. Which of the following is the primary cause of the patient’s lab results?