Abstract: 　Objective　To investigate the clinical and genetic data of a pedigree clinically diagnosed as Joubert syndrome. Method　Clinical data of a patient diagnosed as Joubert syndrome in 2017 was retrospectively analyzed. Whole exome sequencing and sanger sequencing were used to find the causative genes. Results　The 3 months old boy displayed eye movement abnormalities, developmental delay and hypotonia in the four limbs. Cranial MRI showed “molar tooth sign”. The gene sequencing identified a frameshift mutation of c.1411_c.1412insG inherited from his father and a novel missense mutation of c.44A>G in MKS1 gene inherited from his mother. Conclusion　The child has typical clinical features of Joubert syndrome. With Combination of clinical features and gene sequencing, the child was diagnosed as Joubert syndrome.

Key words: Joubert syndrome;　MKS1 gene;　whole exome sequencing;　MRI