Résumé
Background: recent data suggests that monogenic kidney disease may be an underestimated etiology of chronic kidney disease (CKD), given that the underlying cause often remains unknown. Since 2019 adult patients with early onset CKD of unknown etiology (<45 years old), in which both diagnostic yield and clinical impact are expected to be greater, are eligible for a national French genomics program. However few studies have assessed the practical implementation of genetic testing for adults under age 45 with CKD.Methods: we performed an observational study on 502 patients aged 18 to 45 years old referred to a nephrology consultation for CKD at an academic medical center between January 2006 and December 2020. After describing the CKD phenotype and underlying etiology of each patient we established groups in which genetic testing should be performed or discussed based on current recommendations. We then compared characteristics of patients that had undergone genetic testing from onset of CKD to December 2022 to those who had not. Results: glomerular phenotype was predominant (51%), followed by cystic (19%), congenital anomalies of the kidney and the urinary tract (11%), tubulo-interstitial (9%) and vascular (4%) and other (6%) phenotypes. Median age was 36 years, 59% of patients were at early CKD (stage I or II), 39% had a kidney biopsy. Family history of kidney disease was reported in 120 patients (24%) and syndromic features in 21 patients (4%). We identified a strong indication for genetic testing for 92 patients (18%) and a possible one for 60 patients (12%). Amongst them respectively 21 (23%) and 5 (8%) patients had genetic testing. Young age (p=0.01), recent first evaluation (<0.01), family history (p<0.01), syndromic features (p<0.01) and cystic disease (p=0.02) were associated with genetic testing. Most of genetic testing was done by targeted gene panel sequencing. Diagnostic yield was 63% (20 out of 32 patients).Conclusion: 1 out of 5 adults under age 45 with CKD need diagnosis genetic testing according to current recommendations. Only 23% of these had a genetic test, underlining the need for adult nephrologists to be better informed about these new strategies. This study identifies subgroups of patients less likely to be screened. Further guidelines are required to clarify indications and conditions of genetic evaluation of patients with CKD in clinical settings.