Clinical Characteristics And Prognosis Of Patients With Primary Sjögren's Syndrome Secondary To Renal Tubular Acidosis

Objective:This study aimed to establish a single-centered cohort of patients newly diagnosed with primary Sjogren's syndrome-associated renal tubular acidosis(pSS-RTA),and to further describe the clinical characteristics,relevant risk factors,survival and the prognosis of those patients.Methods:We enrolled patients with pSS-RTA newly diagnosed and treated in Peking Union Medical College Hospital.The time of pSS-RTA diagnosis was set as the baseline time,and demographics,clinical presentations,disease assessment and treatment regimens were retrospectively collected,A case-control analysis was also conducted in our study,and those pSS patients without RTA were selected as controls.Then,logistics regression analyses were applied to explore the risk factors of RTA in pSS.Meanwhile,follow-up data was collected.Death or dialysis and renal function deterioration were used separately as endpoints in order to identify related risk factors of survival and poor prognosis of pSS-RTA.Results:There were 182 patients newly diagnosed with pSS-RTA in this study.1)baseline characteristics and subgroup analysis.95.1%patients were female,and the median age of disease onset was 32.2(25.8,42.2)years old.The median baseline age was 39.0(2.0,47.2)years old.RTA and pSS were diagnosed simultaneously in 81.9%patients.I type RTA was more prevalent than other types of RTA,and tubulointerstitial nephritis predominated in pathology.As for treatment,69.0%patients received glucocorticoids,and 49.4%patients received immunosuppressive drugs,among which cyclophosphamide was mostly used.RTA was the first presentation of pSS in 56.0%patients,who had more clinically significant symptoms of RTA and shorter time from SS onset to diagnosis.23.6%patients showed impaired renal function in baseline,the risk factor of which was disease onset age>30 years old(OR=3.225[1.317,7.894])and the protective factor was hypokalemic periodic paralysis(OR=0.206[0.091,0.466]).2)risk factors of RTA in pSS.There were 546 controls enrolled in case-control study.The independent risk factors of RTA in pSS patients included disease onset age?45 years old(OR=8.170[3.508,19.027]),thyroid disease(OR=3.691[1.253,10.872]),interstitial lung disease(OR=4.065[1.046,15.800]),high alkaline phosphatase(ALP)(OR=4.063[1.527,10.814]),elevated immunoglobulin A(OR=3.263[1.440,7.398]),elevated rheumatoid factor(OR=3.854[1.715,8.661])and anemia(OR=2.385[1.071,5.312]),while arthritis(OR=0.211[0.066,0.673])was protective factor.3)prognosis.144 patients were followed in our study,and the mean follow-up time was(8.14±7.76)years.Death or dialysis were recorded in 6 patients.Five-,ten-and fifteen-survival rate were 97.9%,94.9%and 92.0%,respectively.For those with a follow-up time more than 2 years,28/103(27.2%)patients had renal function deterioration,the risk factors of which were the time from RTA onset to diagnosis>1 year(OR=3.610[1.330,9.794]),arthritis(OR=6.256[1.476,26.518])and autoimmune hepatitis(OR=13.302[1.179,150.137]).Conclusions:This study is the largest single-centered cohort of pSS-RTA in the world.In clinical practice,occult SS should be considered when RTA appears before the onset of the characteristic feature of dryness,and pSS patients with risk factors for RTA should be screened,so as to achieve early diagnosis.In addition,for those patients with pSS-RTA complicated with extra-glandular involvements,follow-up and monitoring should be strengthened to improve the survival and prognosis.