A 34-year-old male presents with periorbital edema upon waking for 2 years, lumbago, and physical examination reveals BP 167/93 mmHg, pitting edema in both ankles. Lab findings: Hb 101g/L, UA: protein ++, RBC 10-15/HP, WBC 0-3/HP, 24-hour urinary protein quantification 1.8g, plasma albumin 34g/L, serum Cr 133.8 μmol/L, BUN 10.5 mmol/L. The most likely diagnosis is: