Which is a benign cause of isolated proteinuria?

• A. Positional (orthostatic) proteinuria
• B. Diabetic nephropathy
• C. Glomerulonephritis
• D. Hypertension

Answer: (A)

Isolated proteinuria can be benign when it’s due to orthostatic (positional) proteinuria. This pattern occurs mainly in adolescents: protein in the urine rises during the day when you’re upright and falls back to normal when you’re lying down at night. There’s no decline in kidney function, no edema, and no other signs of kidney disease, so it’s considered a benign finding.

Understanding why helps: the upright position seems to provoke a temporary increase in renal protein loss, but recumbency eliminates it, so a morning sample is typically normal while daytime samples show some protein. This contrasts with conditions like diabetic nephropathy, glomerulonephritis, or hypertensive kidney disease, where proteinuria reflects ongoing kidney injury and is usually accompanied by other abnormalities (blood in the urine, edema, high blood pressure, hyperglycemia, etc.).