A 25-year-old female presents with generalize malaise, lethargy and intermittent low grade fever for 6 month duration. On examination she is pale and erythematous rash is presence on her face and neck. The following are some tests done at the clinic:
Protein ++ Red blood cell: ++ White blood cell: +
ESR 110 (<20 mm/hr )
Creatinine 250 (60-130 umol/L)
Na: 140 (135-145 mmol/L)
K: 5.5 (3.5-4.5mmol/L)
What is the MOST likely cause of her problems?