TRAPPC9-related intellectual disability: report of two new cases

Objectives: Hereditary forms of intellectual disability (ID), an estimated prevalence ranging between 1% and 3% in the general population, are among the most important problems in health care. Especially, autosomal-recessive ID has a very heterogeneous molecular basis and the lack of specific phenotypic features. Here, we report on two different unrelated patients with autosomal-recessive ID and microcephaly. Methods: We have performed array CGH and then sanger sequencing for TRAPPC9 for case 1. We used whole exome sequencing to elucidate molecular diagnosis of case 2. Results: First case has a microdeletion in TRAPPC9 ( 1.7 Mb deletion on chromosome 8q24.23-q24.3[chr8: 139,262,844-141,017,051]) including the last 5 exons of the gene) and c.3435delG [p.Thr1146Profs*8] deletion. We identified the mutations by means of array CGH (aCGH) and Sanger sequencing analysis. Second case has a homozygous missense variant in TRAPPC9: c.623A>C (p.His208Pro) position (NM_031466.8) which is detected by means of whole exome sequencing study of the proband. Conclusion: Our findings suggest that TRAPPC9 gene is a one of the common causes of the ID and it must be investigated especially in the patients with ID, microcephaly and subtle dysmorphic feature.