Stefania Drovandi, Beata S. Lipska-Ziętkiewicz, Fatih Ozaltin, Francesco Emma, Bora Gulhan, Olivia Boyer, Agnes Trautmann, Szymon Ziętkiewicz, Hong Xu, Qian Shen, Jia Rao, Korbinian M. Riedhammer, Uwe Heemann, Julia Hoefele, Sarah L. Stenton, Alexey N. Tsygin, Kar-Hui Ng, Svitlana Fomina, Elisa Benetti, Manon Aurelle, Larisa Prikhodina, Anne M. Schijvens, Mansoureh Tabatabaeifar, Maciej Jankowski, Sergey Baiko, Jianhua Mao, Chunyue Feng, Fang Deng, Caroline Rousset-Rouviere, Małgorzata Stańczyk, Irena Bałasz-Chmielewska, Marc Fila, Anne M. Durkan, Tanja Kersnik Levart, Ismail Dursun, Nasrin Esfandiar, Dorothea Haas, Anna Bjerre, Ali Anarat, Marcus R. Benz, Saeed Talebi, Nakysa Hooman, Gema Ariceta, Franz Schaefer, Lina Maria Serna Higuita, Alaleh Gheissari, Nazym Nigmatullina, Marcin Tkaczyk, Halina Borzecka, Radovan Bogdanovic, Sevgi Mir, Thomas Klopstock, Holger Prokisch, Cornelia Kornblum, Cui-Hua Liu, Shu-Zhen Sun, Yang Dong, Xiao-Wen Wang, Jiang-Wei Luan, Institut Català de la Salut, [Drovandi S] Division of Pediatric Nephrology, Center for Pediatrics and Adolescent Medicine, University of Heidelberg, Heidelberg, Germany. Division of Nephrology, Dialysis and Transplantation, Department of Internal Medicine, Ospedale Policlinico San Martino and University of Genoa, Genoa, Italy. Division of Nephrology, Dialysis, Transplantation, Giannina Gaslini Children's Hospital, Genoa, Italy. [Lipska-Ziętkiewicz BS] Rare Diseases Centre, Medical University of Gdańsk, Gdańsk, Poland. Department of Biology and Medical Genetics, Clinical Genetics Unit, Medical University of Gdańsk, Gdańsk, Poland. [Ozaltin F, Gulhan B] Division of Pediatric Nephrology, Department of Pediatrics, Hacettepe University Faculty of Medicine, Ankara, Turkey. [Emma F] Department of Pediatric Subspecialties, Division of Nephrology and Dialysis, Bambino Gesù Childrens Hospital, IRCCS, Rome, Italy. [Boyer O] APHP, Necker-Enfants Malades Hospital, Pediatric Nephrology, MARHEA and SNI Reference Centers, Paris, France. Imagine Institute, Paris University, Paris, France. [Ariceta G] Servei de Nefrologia Pediàtrica, Vall d'Hebron Hospital Universitari, Barcelona, Spain, and Vall d'Hebron Barcelona Hospital Campus
Coenzyme Q10; Mitochondria; Steroid-resistant nephrotic syndrome Coenzima Q10; Mitocondrias; Síndrome nefrótico resistente a los esteroides Coenzim Q10; Mitocondris; Síndrome nefròtic resistent als esteroides Primary Coenzyme Q10 deficiency is a rare mitochondriopathy with a wide spectrum of organ involvement, including steroid-resistant nephrotic syndrome mainly associated with disease-causing variants in the genes COQ2, COQ6 or COQ8B. We performed a systematic literature review, PodoNet, mitoNET, and CCGKDD registries queries and an online survey, collecting comprehensive clinical and genetic data of 251 patients spanning 173 published (47 updated) and 78 new cases. Kidney disease was first diagnosed at median age 1.0, 1.2 and 9.8 years in individuals with disease-causing variants in COQ2, COQ6 and COQ8B, respectively. Isolated kidney involvement at diagnosis occurred in 34% of COQ2, 10.8% of COQ6 and 70.7% of COQ8B variant individuals. Classic infantile multiorgan involvement comprised 22% of the COQ2 variant cohort while 47% of them developed neurological symptoms at median age 2.7 years. The association of steroid-resistant nephrotic syndrome and sensorineural hearing loss was confirmed as the distinctive phenotype of COQ6 variants, with hearing impairment manifesting at average age three years. None of the patients with COQ8B variants, but 50% of patients with COQ2 and COQ6 variants progressed to kidney failure by age five. At adult age, kidney survival was equally poor (20-25%) across all disorders. A number of sequence variants, including putative local founder mutations, had divergent clinical presentations, in terms of onset age, kidney and non-kidney manifestations and kidney survival. Milder kidney phenotype was present in those with biallelic truncating variants within the COQ8B variant cohort. Thus, significant intra- and inter-familial phenotype variability was observed, suggesting both genetic and non-genetic modifiers of disease severity. In addition, this project has been supported by the European Reference Network for Rare Kidney Diseases (ERKNet), the PodoNet Network for Podocyte Disorders, and the German (mitoNET) and European Networks for Mitochondrial Disorders (GENOMIT). ERKNet is co-funded by the European Union within the framework of the Third Health Programme “ERN-2016 - Framework Partnership Agreement 2017-2021.” PodoNet and mitoNET/GENOMIT have received funding from the German Ministry of Education and Research, and PodoNet from the EU 7th Framework Programme (EURenOmics; grant 2012-305608) and the German Research Foundation (Scha 477/11-1). Founder effect analyses were supported by the Polish Ministry of Science and Education (2017/25/B/NZ2/00519). We would also like to thank Drs. Kei Murayama and Masaru Shimura from Chiba Children’s Hospital, Chiba, Japan, for their contribution to the clinical assessment and follow-up of 2 families. Last but not least, we gratefully acknowledge the help of Elena Levtchenko in rolling out the survey.