Helsmoortel-van der Aa syndrome in a Chinese pediatric patient due to nonsense mutation: A case report.

Background: Helsmoortel-van der Aa syndrome, also known as syndrome, is a condition that causes developmental delay, language impairment, autism spectrum, and variable extraneurologic features. It is caused by heterozygous mutations in the gene on chromosome 20q13. Most of the genetic causes of Helsmoortel-van der Aa syndrome have been reported are as nonsense or frameshift stop mutations in exon 5 of gene, while fewer truncating variants were discovered in exons 4 and the 5' end of exon 5.