Case Presentation: AS is a 39-year-old female with a history of menorrhagia and iron deficiency anemia presenting with stomach cramps. She had a couple of days of nausea, non-bilious, emesis and stomach cramps not associated with menstrual cycles. AS was not experiencing dry mouth, dysphagia or decreased tear production. There was no family history of kidney or autoimmune diseases. Labs were notable for a potassium of 2.1, bicarbonate of 15 and anion gap of 9. Urinalysis revealed sterile pyuria. AS was recently hospitalized 6 weeks ago for menorrhagia during which, her potassium was also low at 2.2. Further workup revealed positive SSA/SSB antibodies. A diagnosis of Primary Sjogren’s Syndrome (pSS) with Type 1 distal renal tubular acidosis (RTA) was made. Rheumatology was consulted and AS was started on a prednisone taper and plaquenil. Potassium was repleted and the patient was continued on potassium and bicarbonate replacement with outpatient Nephrology, Rheumatology and Primary Care follow up.
Discussion: pSS is a chronic autoimmune disease affecting exocrine glands that presents with dry mouth and dry eyes. The prevalence of pSS is roughly 1.3 million individuals ³. Approximately 25% of patients have extra-glandular manifestations that include peripheral neuropathy, interstitial lung disease, cutaneous vasculitis and tubular interstitial nephritis (TIN). pSS precipitates TIN by promoting lymphocytic infiltration of tubular membranes ultimately resulting in RTA. Both Type 1 and Type 2 RTA have been associated with pSS ³. The accompanying acute kidney injury has been shown to the cause of death in 3% of patients with pSS. Our patient had serologic evidence of pSS, signs of renal involvement but no sicca symptoms. One case series showed that 62% of patients with pSS and RTA did not have any other classic symptoms ⁵. The majority of these patients present with hypokalemia. A stud of patients with pSS showed that a 100% of patients with hypokalemia were found to have distal RTA ¹¹. Characteristics of those with pSS and RTA include younger age, less articular manifestations (34% vs. 78%) and less ocular sicca symptoms (62% vs 88%) when compared to those without RTA ⁷. Treatment of extra-glandular pSS primarily involves steroids and immune modulators ⁹. Notably, there is evidence of trends towards improved eGFR and reduced proteinuria with treatment of any kind ¹⁰. Resolution of renal disease was documented in one case report involving a regimen of steroid infusions at 1,000mg per day for 3-days followed by maintenance oral steroids at 24mg per day ¹². In another report, 51% of patients with pSS and elevated serum creatinine >1.2 mg/dL recovered renal function to baseline after treatment with steroids irrespective of immune modulators while 20% had improved renal function ¹¹. With RTA, patients typically require long-term potassium and bicarbonate replacement ⁵. One study noted marked improvement in metabolic derangements with a year of alkali replacement therapy ⁷. Overall, literature review reveals negligible impact of steroids and immune modulators on the electrolyte derangements of distal RTA in pSS but a beneficial impact on kidney function.
Conclusions: pSS has a well-documented association with TIN and RTA. When managing patients with hypokalemia and evidence of RTA, it’s prudent to screen for SSA/SSB antibodies. Doing so can lead to earlier diagnosis of pSS and more timely intervention that may ultimately lead to full preservation of renal function.