MSFinals-2814
A 47-year-old Bangladeshi woman visits her GP complaining of feverish feelings and pains in multiple joints that have persisted for 3 months. She used to work as a nurse in Bangladesh until 8 months ago when she moved to the UK to live with her family. She also reports unintentional weight loss. During the examination, the GP observes signs of an asymmetrical polyarthritis, erythema nodosum on both shins, and firm, enlarged, painless cervical lymph nodes. The patient undergoes several tests, including screening blood tests and joint arthrocentesis with microscopy, culture, and sensitivity (MCS). The results show anti-CCP, RF, and ANA to be negative, CRP to be 31 mg/L (< 5), and no crystals or organisms seen in the MCS joint aspiration sample. What is the most probable cause of her polyarthritis?