Features of distal renal tubular acidosis in Sjögren's syndrome, EXCEPT ONE

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Multiple Choice

Features of distal renal tubular acidosis in Sjögren's syndrome, EXCEPT ONE

In Sjögren’s syndrome, autoimmune tubulointerstitial nephritis can cause distal (type 1) renal tubular acidosis, where the distal tubule can’t secrete hydrogen ions effectively. That leaves urine that remains alkaline (urine pH is inappropriately high, typically >5.5) even though the blood is acidotic. The collecting duct’s inability to acidify also leads to a defect in concentrating urine, so the urine is often dilute with a low specific gravity. The ongoing bicarbonate loss into the urine produces a mild, hyperchloremic metabolic acidosis in the blood. Additionally, patients commonly develop hypokalemia from renal potassium wasting. Therefore, an elevated potassium level would not fit this pattern and is the exception; potassium is usually low rather than high.

In Sjögren’s syndrome, autoimmune tubulointerstitial nephritis can cause distal (type 1) renal tubular acidosis, where the distal tubule can’t secrete hydrogen ions effectively. That leaves urine that remains alkaline (urine pH is inappropriately high, typically >5.5) even though the blood is acidotic. The collecting duct’s inability to acidify also leads to a defect in concentrating urine, so the urine is often dilute with a low specific gravity. The ongoing bicarbonate loss into the urine produces a mild, hyperchloremic metabolic acidosis in the blood. Additionally, patients commonly develop hypokalemia from renal potassium wasting.

Therefore, an elevated potassium level would not fit this pattern and is the exception; potassium is usually low rather than high.

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