Objective To improve the understanding of clinical phenotype and genotype of Allan-Herndon-Dudley syndrome (AHDS). Methods The clinical data of one child with AHDS were retrospectively analyzed and the relevant literature was reviewed. Results A four-month-old male patient born at full term by Cesarean section was 2 . 3 kg weight at birth, and 5 . 6 kg weight and 56 cm length at visit, The muscle tension of the lower extremities was increased, and the head could be raised instantly and the head was tilted back. Whole exon sequencing revealed a hemizygous mutation of c.193 delC in SLC 16 A2 gene in the child. The mutation has not been reported and it could result in the substitution of proline with arginine in amino acid no. 65 and a code shift, and the mutation terminated at the 19 th amino acid after the code shift (p.Pro 65 ArgfsTer19), which might result in a serious impact on the protein function. Family verification showed that the variant was inherited from the mother. Conclusion It is found that the hemizygotic variation of c.193 delC in SLC 16 A2 gene is a novel cause of AHDS.