Renal, Urology and Electrolytesmiddle twist
A 24-year-old man presents with dark brown urine that began the day after the onset of a sore throat. He recalls two similar episodes in the past two years, each with a cold, that cleared within a few days. He has no rash, joint pain or hearing difficulty, and no family member has kidney disease. His blood pressure is 138/86 mmHg. Urine microscopy shows dysmorphic red cells and red cell casts; 24-hour urine protein is 1.1 g. Serum creatinine is 102 µmol/L (60–110), complement C3 and C4 are normal, and antistreptolysin O titre is not raised.
Which one of the following is the most likely diagnosis?