A 32-year-old female presents with proteinuria and hematuria for 3 years. Three years ago, urinalysis (UA) showed protein (+) and 10-20 RBCs/HPF, with blood pressure 125-135/80-90 mmHg and normal renal function. Over 3 years, 24-hour urinary protein quantification ranged 0.6-1.4g. One month ago, she developed sore throat and fever after a cold, followed by gross hematuria. Antibiotics improved her sore throat, but UA still showed protein (++) and 12 RBCs/HPF. Repeat renal function tests showed BUN 10.4 mmol/L and Cr 345 μmol/L. Renal biopsy pathology report: Immunofluorescence: IgG(+), IgA(+++), IgM(-), C3(++), C1q(-), FRA(-), Alb(-), with granular deposits in capillary walls, mesangium, and Bowman's capsule. Light microscopy: 36 glomeruli with diffuse mesangial/endothelial cell proliferation, leukocyte infiltration, severe capillary loop destruction, 18 cellular crescents, 5 fibrocellular crescents, 4 fibrous crescents, tubular atrophy with RBC casts, and interstitial lymphocytic/monocytic infiltration. Diagnosis is: