Clinicopathological Features of Idiopathic Membranous Nephropathy in 33 Adolescents

Objective To investigate the clinicopathological features and prognosis of idiopathic membranous nephropathy(IMN)in adolescents. Methods This was a retrospective study on IMN patients hospitalized between June 2012 and December 2014,and a total of 33 IMN patients aged between 13 and 24 years old were enrolled in the study.Meanwhile,33 IMN patients aged more than 24 years old were selected randomly as control group during the same period.Diagnosis was confirmed by renal biopsy,and the secondary causes of membranous nephropathy were ruled out.Data collected from medical record and biopsy were analyzed. Results In the adolescent IMN group,the mean age at renal biopsy was(20±3)years old,and the male/female ratio was 22/11.Twenty-three cases presented as nephrotic syndrome.Systolic and diastolic pressures were(127±13)mmHg and(77±9)mmHg,respectively.The median 24-hour urine protein was 5.14(3.39,9.31)g/d,and the median serum creatinine was 62(52,73)μmol/L.The positive rate of serum anti-phospholipase A2 receptor in adolescent group was 54%.Compared with control group,the adolescent patients had lower incidence of hypertension and higher baseline estimated glomerular filtration rate level [15.2% vs.39.3%,χ²=4.889,P=0.03;125 ml/(min·1.73m²)vs.100 ml/(min·1.73m²),U=137.5,P<0.001].According to IMN staging criteria in electron microscopy,adolescent patients were classified as one case in stage I,21 in stage Ⅱ,and 11 in stage Ⅲ or higher.The positive rates of IgG1,IgG2,IgG3 and IgG4 subclass staining in glomeruli were 46.9%,3.1%,56.3%,and 87.5%,respectively.Compared with control group,the adolescent patients had lower incidence of renal interstitial fibrosis and arteriolar lesions(6.1% vs.66.7%,χ²=26.19,P<0.001;15.2% vs.66.7%,χ²=18.11,P<0.001).Three patients lost to follow-up while others started steroid combined with cyclosporine A(n=20),cyclophosphamide(n=7),or mycophenolate(n=1)or solely(n=2).After a median follow-up of 18(12,24)months,the median proteinuria decreased to 0.20(0.10,0.42)g/d,whereas serum creatinine level remained stable [69(56.8,81.3)μmol/L].Seventeen patients(56.7%)achieved complete remission(CR),and the remaining 13 patients(43.4%)achieved partial remission(PR).The median time of CR and PR were three and six months,respectively.Only one patient relapsed during the follow-up.Also,21 cases received maintenance therapy including cyclosporine A(n=18),azathioprine(n=2)and mycophenolate(n=1).Conclusions The immunofluorescence IgG subclass in glomeruli and distribution of serum anti-phospholipase A2 receptor in adolescent IMN patients are similar to those in older IMN patients.IMN patients in adolescents responded well to immunosuppressive therapy.Cyclosporine A in low dose as maintenance therapy is effective after achieving remission,and will not increase risk of nephrotoxicity.