Review Question - QID 213719

A 60-year-old man presents to the emergency department after noticing a rash that began in the last 2 days. He states that he has developed a “splotchy rash” on his trunk and arms. Of note, he has also noticed some bleeding from his gums while brushing his teeth this morning. The patient reports no recent sexual contacts, although he mentions that he did have a cold the previous week. On exam, the patient’s temperature is 98.2°F (36.8°C), blood pressure is 128/76 mmHg, pulse is 72/min, and respirations are 14/min. The patient has numerous petechiae on his trunk, arms, and legs, as well as some areas of larger ecchymoses. His labs demonstrate the following:

Hemoglobin: 15.0 g/dL
Leukocytes: 8,000/mm^3
Platelet count: 50,000/mm^3
PT: 12 seconds
aPTT: 30 seconds
Fibrinogen: 240 mg/dL (Normal: 200-400 mg/dL)

Which of the following is the likely mechanism of this disease?