A 28-year-old man presents to his primary care physician with a two-month history of persistent dark-coloured urine and mild lower back pain. He also reports generalized fatigue but denies any fever, weight loss, or recent infections. There is no history of hypertension or diabetes. On physical examination, his blood pressure is slightly elevated at 140/90 mmHg, but there is no significant oedema or other abnormal findings.

Urinalysis reveals gross haematuria and significant proteinuria. Further laboratory tests show normal serum creatinine and estimated glomerular filtration rate (eGFR), suggesting preserved kidney function. A 24-hour urine collection confirms elevated protein excretion of 1.8 g/day. Renal ultrasound shows normal-sized kidneys without any structural abnormalities.

The patient is diagnosed with primary renal haematuric-proteinuric syndrome, likely secondary to glomerular disease. He is started on an ACE inhibitor to manage his blood pressure and reduce proteinuria, along with regular follow-up to monitor his kidney function and the progression of his condition.