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）患者出现肾脏受累的情况较为罕见，其病理改变迄今尚未得到充分阐明。本研究旨在探讨强直性脊柱炎患者肾脏活检的临床表现与病理特征，并对当前相关领域的文献进行综述与讨论。 方法：本研究回顾性分析了1985年10月至2021年3月期间接受肾脏活检的15例高加索人种强直性脊柱炎患者的临床表现与肾脏病理改变。 结果：受试者以男性为主（占比66.7%），肾脏活检时的中位年龄为47岁[四分位间距（IQR）34~62]。就诊时的中位血清肌酐水平为1.3 mg/dL[IQR 0.9~3]，多数患者同时存在蛋白尿（85.7%）和/或血尿（42.8%）。肾脏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（CIN，n=3）与AA淀粉样变性（n=3）；其余诊断包括IgA肾病（IgAN，n=2）、局灶节段性肾小球硬化症（n=2）、膜性肾病（n=1）以及免疫复合物介导的膜增生性肾小球肾炎（IC-MPGN，n=1）。 结论：本研究为目前高加索人种强直性脊柱炎患者中经活检证实的肾脏疾病最大规模队列之一。相较于此前亚洲人群队列的报道，本研究中IgA肾病的患病率更低。相较于既往高加索人群队列研究，本研究中慢性间质性肾炎的患病率更高，而AA淀粉样变性的患病率更低。此外，本研究还首次报道了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。