“Doctor, I am from out of town, my baby is much behind in motor development, please help me”. one day in May 2019, a mother entered the clinic with her baby, the appearance of this little patient caught my attention, with a large head circumference, a wide and prominent forehead, a deformed left hand with six fingers and a deformed left foot with six toes. The doctor’s sensitivity told me that this child was by no means a simple motor developmental backwardness …… The baby was already 2 years and 9 months old and could still only help walk a few steps, had poor balance, couldn’t stand alone, and had obvious cognitive and language backwardness, with no abnormalities found in blood and urine metabolism or gene chip tests. In the afternoon, the mother came over with the baby’s MRI results, which showed bilateral temporal lobe changes and suspected megalencephalic gyrus, please combine with clinical. But why does the baby have poor balance function? After carefully reviewing the films and communicating with the radiologist we found a new problem, the baby’s cerebellar earthworms were not clearly shown, and combined with the baby’s external features, it was likely a genetic related disease, which was later confirmed by gene sequencing that the baby had a G-A mutation in the OFD1 gene chrX:13779311-13779331, associated with the X-linked recessive disorder Joubertsyndrome10 was associated. Joubert’s syndrome is mainly characterized by cerebellar hypoplasia or hypoplasia, respiratory abnormalities in the neonatal period, and delayed motor cognitive development. There is no specific treatment for this disease, but mainly symptomatic treatment and rehabilitation training, and most of this disease has a poor prognosis, about 1/3 die from respiratory failure and 1/3 die from renal failure, therefore, prenatal screening and early diagnosis are of great value in the prevention of this disease.