Distal Renal Tubular Acidosis as Initial Presentation of Sjogren Syndrome in Pregnancy

Introduction: Sjogren's syndrome (SS) is a chronic autoimmune disorder characterized by lymphocytic infiltration of exocrine glands, leading to dryness of mucosal surfaces. While renal involvement in SS is not uncommon, its initial presentation as distal renal tubular acidosis (dRTA) in pregnancy is rare. dRTA is a renal tubulopathy characterized by impaired acid secretion in the distal nephron, resulting in metabolic acidosis. Case Description: A 44-year-old female physician with a history of Hashimoto's thyroiditis was referred to the nephrology clinic for elevated creatinine levels at 19 weeks of gestation without any specific symptoms. Laboratory investigations revealed serum potassium of 3.7 mmol/L, serum CO2 of 12 mmol/L with a normal anion gap of 13, and serum creatinine level of 1.4 mg/dL. Urinalysis showed persistent alkaline urine pH >7. dRTA was suspected and confirmed with 24-hour urine demonstrating undetectably low citrate with ammonium of 14 mmol/24hr. Further rheumatology evaluation revealed positive antinuclear antibodies (ANA), elevated SSA and SSB antibodies, and a positive Schirmer test (right eye 4mm, left eye 4mm) after 5 minutes, suggesting Sjogren's syndrome (SS). Renal US did not show evidence of nephrocalcinosis or hydronephrosis. Treatment with oral potassium citrate 30 mEq twice a day was initiated with normalization of serum CO2 to 23 mmol/L. Kidney biopsy revealed acute on chronic tubulointerstitial nephritis. Consequently, the patient was initiated on prednisone 60 mg/d, followed by a taper. Despite initial clinical improvement, symptoms recurred with prednisone less than 20 mg/d. Azathioprine 50 mg/d was added, and the dose increased gradually while simultaneously tapering off steroids. Significant improvements have been noted in the patient's symptoms and fetal growth, demonstrating a positive shift from the 3rd to the 13th percentile with immunosuppression. Discussion: Extra-glandular renal manifestations are not uncommon presentations of Sjögren's syndrome. SS is associated with various renal manifestations, including tubulointerstitial nephritis and renal tubular acidosis. This case highlights the challenges in managing Sjogren's syndrome during pregnancy and emphasizes the importance of tailored treatment strategies to alleviate the patient's symptoms and mitigate fetal complications.