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A previously healthy 15-year-old boy presented with a 2-week history of lumbar pain and macrohematuria. In the past there was no known hematuria in the patient or his relatives. No psychiatric disturbance was present. His mother had died of uremia. Physical examination was normal; arterial blood pressure was 120/75 mmHg. Laboratory investigations were as follows: no casts in the urinary sediment; blood count normal; renal function normal; proteinuria 310 mg/24 h; blood and urine electrolytes normal; C3 1.25 g/l and C4 0.45 g/l. Calciuria, uricosuria, and oxaluria were normal. Clotting factors were normal. Imaging investigations showed no significant abnormality. Uretrocystoscopy showed no pathological changes. Immunofluorescence of renal biopsy was negative; on light microscopy minor mesangial proliferation was seen in 1 of 12 glomeruli. During 1 year of follow-up the boy maintained good general health, with normal blood pressure and very mild transitory lumbar pain. However, macrohematuria and mild proteinuria (500-600 mg/24 h) persisted. Ultrasonographic follow-up did not show any abnormality. Could this be loin pain hematuria syndrome? What do you advise?.