A case of IgG4-related interstitial nephritis with ureteral obstruction: case report and literature review

In 2001, Hamano et al. found that patients with Autoimmune pancreatitis (AIP) had elevated serum IgG4 concentrations and massive IgG4-positive plasma cell infiltration in the diseased tissues [1]. It was then reported in other organs as a systemic disease. Common anatomic sites affected were the pancreas, salivary gland, lung, periorbital tissues, liver, breast, prostate, thyroid, and kidney. Histologically, it is characterized by an inflammatory infiltrate consisting mainly of lymphocytes and IgG4-positive plasma cells, without cytological atypia, and storiform pattern fibrosis [4,5,6]. In 2007, Zen et al. named such diseases as IgG4-related disease (IgG4-RD) [7], which has been widely recognized internationally. IgG4-RKD is most commonly founded in renal tubulointerstitial nephritis and glomerular diseases, especially membranous nephropathy [2]. However, only a few reports of IgG4-RD appear in the renal pelvis and(or) ureter. However, in this article, we report an unusual case of IgG4-RD.

Combined with this patient, the authors of this paper searched for reports worldwide in the past 20 years on IgG4-RD involving the renal pelvis and(or) ureter (Table 1) [1, 4, 8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]. We found that most were case reports, with most cases reported by Japanese and Chinese urologists. Adding to this case, a total of 36 cases were summarized in the table, of which 26 cases (72.1%) were male, mostly unilateral renal pelvis and(or) ureter involvement(91.7%). Twenty-two patients (61.1%) showed hydronephrosis. Most IgG4-RD involving the ureter showed retroperitoneal fibrosis encasing the ureter, or inflammatory pseudotumor of the ureter, while thickening of the ureteral wall occurs and is easily confused with ureteral malignancies. Ureteral carcinoma was considered in 26 cases (72.2%), but IgG4-RD was pathologically diagnosed after nephroureterectomy or partial ureterectomy. However, only seven patients (19.4%) improved after hormone therapy alone and were not treated surgically. This patient was fortunate; after our discussion and literature search, we highly suspected that the patient's ureteral lesion was IgG4-related, significantly improving after relieving ureteral obstruction and hormone therapy, avoiding the trauma of surgery for the patient.

Table 1 Summary of IgG4-related disease in the renal pelvis and(or) ureter

According to the reports of Ramasamy V et al. [28] and Lei WH et al. [31], IgG4-RD has the possibility of spontaneous remission, manifested as automatic reduction or even regression of ureteral mass. Still, the overall spontaneous remission rate is relatively low. Due to the short follow-up time in most cases, whether there was a recurrence in the late stage of treatment was not mentioned. However, according to the prospective cohort study conducted by Peking Union Medical College Hospital in China between 2011 and 2019, a total of 65 cases were collected IgG4-RD, 14 patients (21.5%) were found to have renal pelvis or ureter involvement, while 16 patients (24.6%) had a re-elevation of serum IgG4 during follow-up. Four patients (6.2%) experienced clinical relapse, and all presented with worsening renal impairment [37]. This patient has been followed up for one year without signs of recurrence. In the case reported by Kim et al. [18], the patient was found to have a ureteral mass considered as IgG4-RD on one side, while ureteral epithelial lymphoma in the reported case by Uehara et al. [19]. The authors stated that MALT lymphoma might be related to IgG4-RD. In addition, Yamamoto et al. [38] reported in 2012 that among 106 patients with IgG4-RD, 11 patients developed malignant tumors during the follow-up period, with the incidence of malignant tumors of 10.4%, significantly higher than that of ordinary people. Therefore, it is recommended that clinicians follow up on all patients diagnosed with IgG4-related diseases for a long time and closely track the possibility of recurrence and the possibility of malignancy.

In conclusion, IgG4-RD can present as a mass in the renal pelvis and (or) ureter, leading to hydronephrosis and resembling a ureteral tumor. Although IgG4-RD may have many clinical manifestations with multiple organ involvement, but there are few reports on such participation of the ureter. Therefore, early recognition of this disease is significant. Most patients respond well to hormonal therapy to avoid surgical treatment due to misdiagnosis as malignant tumors, causing secondary harm to patients.

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