DISCLOSURE:Francesco Emma, Dieter Haffner, Georges Deschênes, Detlef Bockenhauer, Katharina Hohenfellner, Elena Levtchenko, Gema Ariceta, and Lars Pape have declared to have received in the past 36 months consulting fees and/or other honoraria for lectures, presentations, educational events, or participation to advisory boards, from one or more of the following for-profit third parties: Recordati Rare Diseases, Chiesi Pharmaceuticals, and Avrobio. Elena Levtchenko is a board member of Cystinosis Network Europe, Cystinosis Group of The Netherlands & Belgium, and of the Irish Cystinosis Foundation. Francesco Emma and Corinne Antignac are members of the scientific review board of the Cystinosis Research Foundation. All other authors have declared the absence of potential conflicts of interest related to the present work.

AUTHOR CONTRIBUTIONS:The study was designed by Francesco Emma, William van’t Hoff, Patrick Niaudet, Elena Levtchenko, and Olivier Devuyst. Francesco Emma, William van’t Hoff, Katharina Hohenfellner, Rezan Topaloglu, Marcella Greco, Gema Ariceta, Detlef Bockenhauer,, Koenraad Veys, Lars Pape, Sally Hulton, Suzanne Collin, Fatih Ozaltin,, Aude Servais, Georges Deschênes, Robert Novo, Aurélia Bertholet-Thomas, Jun Oh, Marlies Cornelissen, Mirian Janssen, Dieter Haffner, Patrick Niaudet and, Elena Levtchenko have taken care of patients and have collected data. Chiara Bettini and Francesco Emma have created the final database and have verified all data entry. Francesco Emma, Koenraad Veys, and Corinne Antignac have reviewed and classified the genetic data. Data analysis and interpretation was performed by Francesco Emma, Elena Levtchenko and Olivier Devuyst. Statistical analysis was performed by Francesco Emma and Lucilla Ravà. The manuscript was drafted by Francesco Emma and Elena Levtchenko and reviewed by all authors. All authors have provided significant intellectual contributions to the manuscript and have approved the final version.