Kidney Stones Reveal an Autoimmune Culprit

Introduction: Nephrolithiasis (NL) can occur from an array of reasons including dehydration, dietary intake, metabolic disorders, diuretic use as well as autoimmune conditions. Renal tubular acidosis (RTA) classifies several conditions, in which metabolic acidosis is caused by defects in renal tubular hydrogen ion secretion. Nephrolithiasis is caused only in Type I RTA. When related to autoimmune conditions such as Sjogren’s Syndrome (SS) it is called Secondary Type I RTA. Case Description: An 18 year old female with no past medical history initially presented for progressive anterior neck swelling, diagnosed as parotitis. Four years later, she returned with severe flank pain, radiating to all abdominal quadrants, nausea, vomiting and fever. A CT scan of the abdomen and pelvis revealed multiple bilateral intrarenal and ureteral junction calculi, perinephric stranding and hydronephrosis, consistent with obstructive nephropathy, complicated by pyelonephritis. Stone analysis demonstrated 90% calcium phosphate and 10% calcium oxalate monohydrate composition. Over the following year the patient presented six additional times with similar complaints and imaging confirmed new obstructive stones with similar composition requiring repeat cystoscopy with ureteral stent placement. The patient continued to have episodes of recurrent NL, but developed xerophthalmia and dysphagia, particularly to solids two years later. Laboratory evaluation revealed persistently elevated urine pH >5.5, elevated anion gap and low serum bicarbonate level during each episode of nephrolithiasis. Autoimmune workup was initiated due to xerophthalmia, revealing positive SS-A antibodies, anticardiolipin IgG, Antinuclear antibody and elevated inflammatory markers. A minor salivary gland biopsy demonstrated foci of periductal lymphocytic aggregates, consistent with SS. Discussion: Renal involvement in Sjogren's Syndrome is rare especially in adolescents, affecting <10% of patients. The underlying pathophysiology of dRTA in SS is poorly understood but the lack of Hydrogen-ATPase in the cortical collecting tubule, failure of the proton pump and defective permeability causing bicarbonate leakage have been suggested. In a retrospective study of 68 patients with anti SS-A antibody positivity, 33% had a history of nephrolithiasis. Based on this case, recurrent nephrolithiasis in adolescents should raise suspicion for SS.