Whole-exome sequencing identified first homozygous frameshift variant in the COLEC10 gene in an Iranian patient causing 3MC syndrome type 3.

Background: 3MC syndrome type 3 is an autosomal recessive disorder caused by mutations in the COLEC10 gene besides other genes like COLEC11 and MASP1. This disorder is characterized by facial dysmorphism, cleft lip and palate, postnatal growth deficiency, cognitive impairment, hearing loss, craniosynostosis, radioulnar synostosis, genital and vesicorenal anomalies, cardiac anomalies, caudal appendage, and umbilical hernia.

Methods: In the present study, whole-exome sequencing was performed in order to identify disease causing variant in an Iranian 7-year-old affected girl with craniosynostosis, dolichocephaly, blepharoptosis, clinodactyly of the 5th finger, high myopia, long face, micrognathia, patent ductus arteriosus, downslanted palpebral fissures, telecanthus, and epicanthus inversus. Identified variant confirmation in the patient and segregation analysis in her family were performed using Sanger sequencing method.

Results: A novel homozygous frameshift deletion variant [NM_006438.5: c.128_129delCA; p.(Thr43AsnfsTer9)] was identified within the COLEC10 gene. Up to now, only three 3MC syndrome patients with mutations in the COLEC10 gene have been reported, and here, we report the fourth patient and the first homozygous frameshift variant.

Conclusion: Other genes and factors responsible for 3MC syndrome occurrence are remained to be discovered. We believe further investigation of the genes in the lectin complement pathway is needed to be done for the identification of other causes of this disease.