Case report: Neonatal diabetes mellitus with congenital hypothyroidism as a result of biallelic heterozygous mutations in GLIS3 gene

Neonatal diabetes mellitus with congenital hypothyroidism (NDH) syndrome (MIM# 610199) is a rare disease caused by autosomal recessive mutations in the GLIS3 gene. GLIS3 is an important transcription factor that might acts as both a repressor and activator of transcription. To date, 22 cases of NDH syndrome from 16 families and 11 countries have been described. Herein, we report a child who developed diabetes during the first week of age. Additionally, she suffered from congenital hypothyroidism, cardiac abnormalities, and polycystic kidney disease. Genetic analysis revealed that patient is a carrier of two novel heterozygous mutations, p.Pro444fsdelG (c.1330delC) and p.His647Arg (c.1940A > G) in the GLIS3 gene. Each was inherited from clinically healthy father and mother, respectively. Bioinformatic tools (SIFT, PolyPhen2, PROVEAN and SWISS-MODEL) declared that the p.His647Arg (c.1940A > G) variant has strong detrimental effect and disturbs Kruppel-like zinc finger domain. All but one so far described cases of NDH syndrome have been caused by homozygous of GLIS3, making the described case the second case of pathogenic, compound heterozygosity of GLIS3 worldwide posing substantial clinical novelty and detailing an interesting interplay between the observed variants and GLIS3 expression, which seems to be autoregulated. Hence, the damaging missense mutation may further reduce the expression of any remaining functional alleles. This case report expands our understanding of the clinical phenotype, treatment approaches, and outcome of infants with GLIS3 mutations and indicates the need for further research to deepen our understanding of the role of GLIS3.