Nephrocalcinosis in Sjögren's syndrome: a late sequela of renal tubular acidosis

Sjögren's syndrome (SS) is an autoimmune exocrinopathy that develops into systemic autoimmune disease in 25% of patients, leading to general complications, one of which is kidney involvement. It presents mainly as interstitial nephritis, disclosed by hyposthenuria, distal renal tubular acidosis (RTA) and diabetes insipidus. We here describe five cases of SS with type-1 RTA (hyperchloraemic metabolic acidosis with an anion gap and alkaline urine pH) who developed nephrolithiasis, nephrocalcinosis and renal insufficiency. Hypercalciuria due to acidosis was the main nephrocalcinosis-prone factor in four patients; four subjects displayed diminished renal concentrating capacity, and two had hypokalaemia.