Characteristics and Outcome of Immunoglobulin A Nephropathy - a Swiss single center experience

BackgroundImmunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Geographic differences in disease course and treatment response are well recognized. The purpose of this analysis was to study clinical and histological characteristics, treatment practices and outcome of IgAN cases from a Swiss tertiary center. MethodsThis retrospective cohort analysis identified 158 cases of adult biopsy-proven IgAN by chart review diagnosed between 1980 and 2017. Following detailed phenotypisation, standard descriptive methods and univariate analysis corrected by the Bonferroni method were applied. ResultsPatients were majorly male and of Caucasian descent. At diagnosis, mean estimated glomerular filtration rate (eGFR) was 55.4 ml/min/1.73 m2, mean proteinuria was 2.4 g/d, 69.9% of the patients were hypertensive. Clinical presentation varied according to age. Initial biopsies showed moderate to severe tubular atrophy and interstitial fibrosis (IFTA) in 29.1% and crescents in 36.7% of cases. Therapy included renin-angiotensin-aldosterone-inhibitors in 86.7%, immunosuppressive therapy in 46.8% including steroids and other immunosuppressive drugs (28.7%), mainly azathioprin. Outcome included 34.1% complete and 22.2% partial remissions, relapses in 32.0% of patients, while 43.0% of patients progressed to ESKD during follow-up (median 100.0 months). Recurrence rate after transplantation was 18.8%. Immunosuppressive therapy was more frequently used in patients with higher proteinuria level and crescents. Predictors of progression were lower eGFR, higher proteinuria and higher extent of IFTA on the initial biopsy. ConclusionsThis retrospective cohort analysis gives insight into characteristics and outcome of patients with IgAN from a Swiss tertiary center, treatment practices as well as predictors of outcome and therapy choices. Key learning pointsO_ST_ABSWhat was knownC_ST_ABSO_LIA wide range of clinical presentations exists for immunoglobulin A nephropathy (IgAN) pointing to IgAN as a disease spectrum rather than a single disease entity C_LIO_LIAdditional important geographic differences regarding disease prevalence, disease course and response to therapies have been recognized C_LIO_LIProgression to end-stage kidney disease (ESKD) occurs in a substantial part of affected patients C_LI This study addsO_LIIn this cohort, a comparatively high proportion of patients was treated by immunosuppressive therapy including non-steroid treatment underlining the heterogeneous nature of treatment practices worldwide C_LIO_LIPredictors of the use of immunosuppressive therapy in this cohort have been identified C_LIO_LISimilarly to recent UK registry data, a high rate of progression to ESKD has been found including patients with low baseline proteinuria level C_LI Potential impactO_LIThese findings further underline the importance of achieving an improved characterization and pathogenetic understanding of IgAN disease subtypes through ongoing research efforts C_LIO_LIAt the beginning of the current new therapeutic era for patients with IgAN, this goal has now become more relevant than ever C_LI