Kidney Disease in Ankylosing Spondylitis: a case series and review of the literature

Abstract Background Kidney disease is a rare manifestation of ankylosing spondylitis (AS) and its pathological alterations remain poorly described. The aim of this study was to investigate the clinical presentation and pathological alterations on kidney biopsy of AS patients and review and discuss the current literature on the issue. Methods: We retrospectively studied the clinical presentation and kidney pathological alterations of 15 Caucasian AS patients submitted to kidney biopsy between October 1985 and March 2021. Results: Patients were predominantly male (66.7%) with median age at the time of kideney biopsy of 47 years [IQR 34 - 62]. Median serum creatinine at presentation was 1.3 mg/dL [IQR 0.9 - 3] and most patients also had either proteinuria (85.7%) and/or hematuria (42.8%). The most common indication for kidney biopsy was nephrotic syndrome (33.3%), followed by acute or rapidly progressive kidney injury (20%) and chronic kidney disease of unknown etiology (20%). Chronic interstitial nephritis (CIN) (n=3) and AA amyloidosis (n=3) were the most common diagnosis. Others included IgA nephropathy (IgAN) (n=2), focal segmental glomerulosclerosis (n=2), membranous nephropathy (n=1), and immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN)(n=1). Conclusions: We present one of the largest series of biopsy-proven kidney disease in Caucasian AS patients. We found a lower prevalence of IgAN than previously reported in Asian cohorts. We found a higher prevalence of CIN and a lower prevalence of AA amyloidosis than that described in previous series of Caucasian patients. We also present the first case of AS-associated IC-MPGN.

摘要 背景 强直性脊柱炎（ankylosing spondylitis, AS）累及肾脏的情况较为罕见，其病理改变的相关研究仍较为匮乏。本研究旨在探讨强直性脊柱炎患者肾脏受累的临床表现及肾活检（kidney biopsy）病理特征，并对当前该领域的相关文献进行综述与探讨。
方法 本研究回顾性分析了1985年10月至2021年3月期间，15例接受肾活检的白种人强直性脊柱炎患者的临床表现与肾脏病理改变。
结果 纳入患者以男性为主（占比66.7%），接受肾活检时的中位年龄为47岁[四分位间距（interquartile range, IQR）34~62]。就诊时的中位血清肌酐水平为1.3 mg/dL[四分位间距0.9~3]，多数患者合并蛋白尿（85.7%）和/或血尿（42.8%）。肾活检最常见的指征为肾病综合征（33.3%），其次为急性或快速进展性肾损伤（20%）以及病因不明的慢性肾脏病（20%）。最常见的病理诊断为慢性间质性肾炎（chronic interstitial nephritis, CIN，n=3）与AA型淀粉样变性（AA amyloidosis，n=3）；其余病理类型包括IgA肾病（IgA nephropathy, IgAN，n=2）、局灶节段性肾小球硬化症（focal segmental glomerulosclerosis，n=2）、膜性肾病（membranous nephropathy，n=1）以及免疫复合物介导的膜增生性肾小球肾炎（immune complex-mediated membranoproliferative glomerulonephritis, IC-MPGN，n=1）。
结论 本研究为目前纳入白种人强直性脊柱炎患者肾活检确诊肾脏疾病的最大队列之一。本研究发现，IgA肾病的患病率较此前亚洲队列的报道更低；与既往白种人患者队列相比，本研究中慢性间质性肾炎的患病率更高，而AA型淀粉样变性的患病率更低。此外，本研究还报道了首例与强直性脊柱炎相关的免疫复合物介导膜增生性肾小球肾炎病例。