Joubert syndrome (JS) is a complex, genetic, neurological disorder which includes a specific cerebellum malformation. Multiple genes are implicated in this disease. It is known to be a severe disorder because it causes important neurodevelopmental disabilities and other complications such as low vision, kidney disorder and liver fibrosis. In our French cohort, JS patients caused by CC2D2A mutations, had encouraging neurodevelopmental features and a low rate of other organ disorders. In this study, we built a correlation with one particular homozygous mutation on the CC2D2A gene which was linked to a worse developmental outcome with renal and vision complications. This study encompasses the largest cohort of JS patients caused by CC2D2A mutations and details their clinical manifestations. It will allow practitioners to establish specific monitoring recommendations for these JS patients and to give out specific prognosis information to patients and their families, especially when the need for prenatal testing occurs. (By Madeleine Harion, https://jmg.bmj.com/content/early/2022/11/01/jmg-2022-108754 )