 This case study reports a rare form of modi type 4, caused by a PDX1 mutation in a 10-year-old Korean girl. The patient presented with non-ketotic diabetes mellitus, but did not have any other symptoms associated with type 2 diabetes. Genetic testing revealed a heterozygous pathogenic PDX1 mutation, P.GLY246-ARXTER21, indicating that this variant arose de novo in the patient. Despite being treated with metformin alone, the patient's HBA1C levels remained high, so she was also prescribed insulin deglutic in addition to metformin. This case study highlights the importance of genetic screening in patients with modi characteristics, as it can help identify rare forms of modi such as modi type 4 caused by PDX1 mutations. This article was authored by Jimmy M Park, Soo Young Lee, Ja Young Seo, and others.