system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 66-year-old man presents to the outpatient department complaining of a rash similar to the ones in the image. The skin lesions have been present for about 2 weeks. It is present in the buttocks and both inferior limbs. There is no association of skin lesions with exposure to sunlight or medication use. The patient also reports joint pain affecting the distal and proximal joints in both the upper and lower limbs. The joint pain has been present for about a week and seems to improve with Tylenol use. The patient is a retired armed force personnel with an extensive tour of overseas duty. He received blood transfusion following a career-ending injury about 30 years ago. He denies alcohol and tobacco use. He is currently in a monogamous relationship with his wife for 40 years. His past medical history is significant for hypertension controlled on Enalapril. Physical examination shows mild pallor, multiple palpable purpuric lesions with occasional ulcerations bilaterally in the upper and lower limbs. Pulse rate is 88/min and blood pressure is 128/82 mm Hg. Laboratory test findings are:
HIV I and II antibodies negative
Rheumatoid factor positive
Hepatitis C antigen positive
Hepatitis B surface antigen positive
Hepatitis B antibody positive
Anti-neutrophil antibody positive
Hematocrit 38%
Which of the following mechanisms is most likely responsible for his clinical presentation?
assistant
Virus-induced clonal expansion of autoreactive B lymphocytes