The genetics of macrocephaly, autistic spectrum disorders and developmental delay in Chinese children

Abstract

Objective: Macrocephaly is a common dysmorphic feature in children with autistic spectrum disorders and developmental problems. Previous studies showed that 14–34% of autistic children had head circumference >97 percentile. The aim of this study was to investigate the genetic causes of children with macrocephaly, autistic spectrum disorders and/ or global developmental delay. Method: Chinese children diagnosed with macrocephaly with head circumference >2 S.D. with either autistic spectrum disorders and/ or global developmental delay were recruited prospectively from 1st January 2010 to 31st December 2014. After obtaining informed consent, whole exome sequencing was done on the patients’ blood and buccal DNA. There were total of 18 patients and 27 family members. Coding exons in DNA samples from the patients and the family members were captured by Illumina Truseq Exome Enrichment Kit (64mb) and sequenced by Illumina Hiseq 2000 machine. The whole sequencing data analysis follows the best practice of GATK 3.2 (The Genome Analysis Toolkit, Broad Institute). Results: Out of the 18 patients with macrocephaly, autistic spectrum and/ or global developmental delay, 5 patients (27%) were identified to have genetic mutations (3 de novo mutations, 1 autosomal dominant and 1 was X-linked inherited). 4 out of the 5 mutations were linked to the PI3KAKT- mTOR pathway. Interestingly, one of these patients with biallelic PTEN mutations had the most severe clinical features of macrocephaly, global developmental delay and early death. Conclusion: Children with macrocephaly, autistic spectrum disorders and/ or global developmental delay should be offered genetic evaluations to rule out megalencephaly syndromes related to the PI3K-AKT-mTOR pathway. Early recognition will help to identify and treat complications such as increased cancer risks and early lethality.