Bardet-Biedl syndrome (BBS) is a rare ciliopathic human genetic disorder with mainly an autosomal recessive inheritance. BBS phenotype develops over the years and diagnosis is usually made in late childhood or early adulthood. Prenatal diagnosis is rare in the absence of family history or consanguinity. We present a prenatal case without a family history of inherited diseases or consanguinity. Mid-trimester ultrasound revealed hyperechogenic kidneys and postaxial polydactyly putting us on track of BBS. The fetopathology supported this diagnosis and the whole-exome sequencing confirmed the hypothesis. Our case illustrates how high-resolution obstetric scan, detailed observation of fetal features and application of gene sequencing technology contribute to elucidate the aetiology of rare, yet disabling and incurable disease, with the particular setting of negative family history.

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