Long-term morbidity of IgA nephropathy in children evaluated with newly proposed remission criteria in Japan.

backgroundThe long-term outcome of pediatric IgA nephropathy (IgAN) is unclear. Objective IgAN remission criteria were proposed by the Japanese Society of Nephrology in 2013.

methodsChildren with newly developed IgAN followed for >5 years were analyzed. They were divided into two groups based on histological findings at initial kidney biopsy: the focal mesangial proliferation group (Focal group) and diffuse mesangial proliferation group (Diffuse group). The primary outcome was the remission rate according to the newly proposed IgAN remission criteria.

resultsThe patients comprised 53 children (31 boys; mean age at IgAN onset, 10.0 years). The Focal and Diffuse groups comprised 21 and 32 patients, respectively. No significant differences in patient characteristics were found between the groups except for steroid administration. The median follow-up period from onset was 9.9 years. Sixteen patients in the Diffuse group and 10 in the Focal group had not achieved remission at the last observation. Patient conditions 2 years after the initial treatment were almost identical to those at the last observation. Multivariate analysis revealed that proteinuria, particularly <0.5 g/g Cr at 2 years, was significantly associated with remission at the last observation regardless of proteinuria status at the start of treatment.

conclusionsPediatric IgAN has a prolonged course that is longer than expected regardless of severity at diagnosis. Patient conditions 2 years after initial treatment predicted their conditions at the last observation. Although the final renal function of these patients is presently unclear, children with IgAN should be followed beyond adolescence and further into adulthood.