A synonymous variant in KCNJ11 leading to MODY13: a case report and literature review

Abstract 137words Background: MODY13 (Maturity-onset diabetes of the young, type 13) is monogenic diabetes associated with the KCNJ11 mutation rarely reported to date. A patient with c.843C>T(p.L281=) in the KCNJ11 gene is reported only in a Chinese patient with congenital hyperinsulinemia. There is no patient diagnosed with MODY13 carrying a synonymous heterozygous variant in the KCNJ11 reported till now. Method: We followed a 9-year-old boy presenting ketosis and diagnosed with MODY13. Whole-exome sequencing (WES) and Sanger validation were performed on the proband and his parents, respectively. Then bioinformatics software was used to predict the RNA structure and protein function. Result: The clinical characteristics and genetic traits of a 9-year-old boy with MODY13 are described in this study. WES revealed the synonymous heterozygous variant c.843C>T (p.L281=) in the KCNJ11 exon 1 in this patient, which prompted the opposite phenotype previously described. The patient and his mother who carries c.843C>T have morphologically comparable RNA structures of KCNJ11 which is completely separated from his mother. Conclusion: A c.843C>T (p.L281=) variant in the KCNJ11 gene contributes to MODY13. In clinical practice, WES should be applied to diagnose hyperglycemia in patients without characteristic clinical symptoms of diabetes to improve prognosis.