Abstract: Objective To explore the clinical and genetic characteristics of MED 13 L syndrome caused by the mutation of MED 13L gene. Method The clinical data of MED 13 L syndrome in 2 children were retrospectively analyzed. Peripheral blood samples were collected from the children and their parents for gene chip and high-throughput sequencing analysis. The chromosome microdeletions/microduplications were verified by RT-PCR, and gene variations were verified by Sanger sequencing. Results The two patients were boys, aged 2 years 6 months and 4 years 3 months, respectively. Both had special facial features, including oblique head deformity, eyelid ptosis, wide eye distance, flat bridge of nose and sinking corners of mouth. Both had language retardation, motor development retardation, low muscle tension, moderate and mild mental retardation. Case 1 also had ventricular septal defect, and case 2 had polydactyly, autism and dysplasia of corpus callosum, etc. Gene chip analysis results showed that case 1 had a 1 . 42 MB deletion in 12 q 24 . 2 region, and RT-PCR showed no abnormality in the same region of her parents. High throughput sequencing showed that the MED13L gene of in case 2 had heterozygous variation of c.580g > t (p.e 194 x), which had not been reported. Sanger verified that neither parent was abnormal. Conclusion MED 13 L syndrome is characterized by special facial features, retardation in language and, motor, and mental retardation., Sand some MED 13 L syndrome is associated with congenital heart disease, bone abnormalities and behavioral abnormalities. There was a MED 13 L gene abnormality exists and . Aa new mutation which has not been reported has beenis found which has not been reported.

Key words: MED 13 L syndrome; MED 13 L gene; gene mutation