Tohoku J. Exp. Med., 2021 February, 253(2)

Incidence and Relapse Triggers of Childhood Idiopathic Nephrotic Syndrome between 2006 and 2016: A Population-Based Study in Fukushima, Japan

Yohei Kume,1 Yukihiko Kawasaki,1,2 Kazuhide Suyama,1 Ryo Maeda,1 Yui Takahashi,1 Masato Hoshino,1 Shigeo Suzuki,3 Masaki Mitomo,4 Ruriko Nozawa,5 Yoshiyuki Namai,6 Hiroko Sakuma,7 Masatoshi Kaneko,8 Shinichi Oda,9 Hiromichi Murai,10 Shuto Kanno,10 Katustoshi Nagasawa,11 Masaki Ito,12 Hoshiro Suzuki,13 Shinichiro Ohara,13 Hayato Go,1 Aya Goto14 and Mitsuaki Hosoya1

1Department of Pediatrics, Fukushima Medical University, Fukushima, Fukushima, Japan
2Department of Pediatrics, Sapporo Medical University, Sapporo, Hokkaido, Japan
3Department of Pediatrics, Ohara General Hospital, Fukushima, Fukushima, Japan
4Department of Pediatrics, Japanese Red Cross Society Fukushima Hospital, Fukushima, Fukushima, Japan
5Department of Pediatrics, Fujita General Hospital, Date-gun, Fukushima, Japan
6Department of Pediatrics, Ohta Nishinouchi General Hospital, Koriyama, Fukushima, Japan
7Department of Pediatrics, Hoshi General Hospital, Koriyama, Fukushima, Japan
8Department of Pediatrics, Jusendo Hospital, Koriyama, Fukushima, Japan
9Department of Pediatrics, Iwase General Hospital, Sukagawa, Fukushima, Japan
10Department of Pediatrics, Shirakawa Kosei General Hospital, Shirakawa, Fukushima, Japan
11Department of Pediatrics, Takeda General Hospital, Aizuwakamatsu, Fukushima, Japan
12Department of Pediatrics, Soma General Hospital, Soma, Fukushima, Japan
13Department of Pediatrics, Iwaki City Medical Center, Iwaki, Fukushima, Japan
14Center for Integrated Science and Humanities, Fukushima Medical University, Fukushima, Fukushima, Japan

Childhood idiopathic nephrotic syndrome (NS) is defined by proteinuria and hypoproteinemia. The incidence of childhood idiopathic NS varies with age, race, residential areas, and social conditions. In Japan, its incidence was estimated to be 6.49 cases/100,000 children. Our study aimed to investigate the incidence, characteristics, and rate of relapse of idiopathic NS in Fukushima between 2006 and 2016. Overall, 158 children aged from 6 months to 15 years old (65.8% male) developed idiopathic NS (median age at onset, 5.3 years). The peak age at onset was three years. The average annual incidence of childhood idiopathic NS was 5.16 (range, 3.47-9.26) cases/100,000 children. The highest incidence was in 2011, which was the year of the Great East Japan Earthquake and nuclear power plant accident, and reportedly caused psychological distress in the children at the time. Conversely, the five-year birth cohort showed minor difference from 2008 to 2012. The rate of incidence in males aged < 5 years was thrice greater than in females of the same age and almost the same for males and females aged 11-15 years. Of 507 total relapses in 115 NS children, common triggers of relapses were steroid discontinuation or reduction and infection. The average annual incidence of childhood NS based on the Fukushima population was lower than previously reported in Japan, and the annual incidence has changed over an 11-year period. These changes may be affected by social or environmental factors, including mental stress associated with lifestyle changes after the disaster.

Keywords —— hypoproteinemia; idiopathic nephrotic syndrome; incidence; proteinuria; relapse

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Tohoku J. Exp. Med 2021 February, 253(2), 125-134.

Correspondence: Yohei Kume, Department of Pediatrics, Fukushima Medical University, 1 Hikarigaoka, Fukushima, Fukushima 960-1295, Japan.

e-mail: kumetti@fmu.ac.jp