Joubert syndrome is characterized by clinical and genetic heterogeneity and is associated with mutations in the following genes: INPP5E, NPHP1, AHI1, CEP290, CSPP1, TCTN3, MKS11, MKS10, MKS9, TCTN2, NPHP3, CC2D2A, RPGRIP1L, MKS4, TMEM67, TMEM216, MKS1, CEP120, C2CD3, B9D2, B9D1, MKS1, PDE6D, IFT172, TCTN3, C5ORF42, TMEM231, TMEM138, CEP41, TMEM237, KIF7, TCTN1, OFD1, and ARL13B68. This evidence concerns the gene B9D1 and Joubert syndrome.