Q. A 28-year-old female presents to the emergency department with complaints of fever, fatigue, a rash on her face (see image), and swelling in her hands and feet. She also describes the presence of “foamy” urine and nocturia. The patient has a past medical history significant for systemic lupus erythematosus, which was diagnosed two years ago, and for which she takes hydroxychloroquine and prednisone. On physical examination, the patient appears fatigued and has a malar rash on her face. Her vital signs are within normal limits. The patient’s cardiopulmonary assessment is unremarkable. Her abdomen is soft, and non-tender, with no masses appreciated. Joint examination reveals tenderness and swelling in multiple joints, including her wrists, hands, and knees. Mild peripheral edema is also noted. You order blood work, a urinalysis, and a renal ultrasound. Laboratory results show a positive ANA, an elevated erythrocyte sedimentation rate, low complement levels, and a positive anti-dsDNA antibody test. The patient's urine dipstick shows 3 plus protein and 1 plus blood. The urine protein to creatinine ratio is 1.5, and a renal ultrasound shows bilateral renal cortical thinning. Based on the information you have at this point in time, which of the following is the most likely underlying etiology of her symptoms?