Patients’ demographic characteristics
A total of 132 patients diagnosed as RPF were enrolled in this study. Among the 132 cases in our cohort, 47 patients (35.6%) were classified as having IgG4-related RPF (19 definite, 5probable, 23possible), and 85 patients were classified as having IRPF. The demographic features of all cases are shown in Table1. The mean age at disease onset was 54.8 years, and 70% patients were male. Sixty-four patients (48.4%) underwent biopsies. Among them, 24 cases were identified as IgG4-related RPF, and 40 cases were identified as IRPF. Established allergic diseases were found in fourteen cases(10.6%).Cardiovascular disease risk factors, i.e. hypertension, diabetes mellitus, and smoking, were found in 40 (30.3%),21 (15.9%), and 60(45.4%) patients, respectively.
We compared the demographic features of patients with IgG4-related RPF against cases of IRPF in Table2. The gender ratio (Male:Female) of IgG4-related RPF group and IRPF group were 4.8:1 and 1.7:1, respectively (P=0.012).The time from disease onset to diagnosis was 26 months in IgG4-related group, which was significantly longer than that in IRPF group (12 months) (P=0.001). The mean follow-up time of IgG4-related RPF group and IRPF patients was 20 months and 24months, respectively. In terms of allergic disorders, IgG4-RD RPF patients (21.2%) had a higher frequency of allergic diseases (allergic rhinitis, urticaria, asthma) than that in IRPF patients (4.7%) (P=0.006).
Clinical symptoms varied from patient to patient. Pain was the most common presenting symptom. Sixty-four patients (48.4%) had lower back pain, which was more common in IRPF group(P=0.035). Thirty-five patients (26.5%) had flank pain and twenty-seven (20.4%) had abdominal pain, respectively. Hydronephrosis occurred in 85 of 132 patients (64.3%), with 35 bilateral and 50 unilateral involvement，however, there was no statistical difference between this two groups. Other constitutional symptoms were fever, weight loss, lower limb edema, venous thrombus , and anorexia (Table 3).Organ involvement was evaluated by systematic standards including symptoms, signs, radiographic or other image examinations. Although 42 of 47 patients (89.3%) with IgG4-related RPF had other organ involvement, with the pancreas being the most commonly affected organ, there were no patients in the IRPF group with other organ involvement ( P<0.001). However, there was no significant difference in incidence of mass location (P=0.482).
We further compared the laboratory tests between these two groups (Table 4). The levels of inflammatory markers such as ESR and CRP were not statistically different between groups, while the number of patients with elevated CRP was significantly higher in the IRPF group (61.1% vs 42.5%,P=0.04). Hypocomplementemia was a common finding in both IgG4-related RPF (21.2%) and IRPF group (18.8%) (P=0.734), and the number of patients with low serum C4 was significantly higher in IgG4-related RPF group (P=0.024). The serum IgG4 level and IgE level were significantly higher in IgG4-related RPF group. IgG4-related RPF patients were more commonly associated with elevated eosinophils counts (23.4% vs 7.05%, P=0.007).
Treatment strategies are reported in Table 5. However, there was no significant difference in both groups. As shown, fifteen patients (11.4%) received no treatment, whereas other patients received medical therapy (31.8%), surgical therapy (9.1%), or both (47.7%). Glucocorticoids are the first-line medical therapy, with initial doses of 0.75–1mg/kg per day of prednisone in our study. About 79.5% of all our patients were initially treated with prednisone. Immunosuppressants used in our cohort comprised cyclophosphamide alone in 46 patients (34.8%), Methotrexate alone in 3(2.2%)patients, and mycophenolate mofetil in twenty(15.1%) patients. Eleven patients (8.3%) experienced immunosuppressant replacement during the period, because of either side effects or poor efficacy. Two patients received rituximab combined with glucocorticoids, due to disease relapse. Tamoxifen was used alone in twelve (9.0%) patients.
With regard to surgical interventions, 55 patients (41.6%) had ureteral stents to help alleviate the symptoms. Ureterolysis was carried out in 18 of 132 patients. Fourteen patients (10.6%) underwent percutaneous nephrostomy.