SIX1 and renal dysplasia: Dynamic monitoring of kidney size is particularly important for prenatal diagnosis of renal dysplasia.[16,17] There are many mechanisms leading to congenital urinary system abnormalities, among which chromosome abnormality and gene mutation are the most important causes.[18] Some BOR pathogenic genes, including EYA1 (8q13.3), SIX1 (14q23.1), and SIX5 (19q13.32) have been identified.[6,19,20] Among them, EYA1 is the first identified and the most common pathogenic gene that causes BOR.[6] Nearly about 40% of BOR patients have EYA1 mutations.