MODY-4 is an uncommon monogenic autosomal dominant diabetes type induced by several heterozygous mutations, associated with early onset type 2 diabetes mellitus without any non-pancreatic sequelae. The MODY-4 gene involved is PDX1 (pancreatic and duodenal homeobox 1) and it encodes a transcription factor also referred to as “insulin promoter factor-1” or “IPF-1”, fundamental for the development and function of pancreatic cells and, specifically, beta-cells. Moreover, PDX1 gene is fundamental for insulin release prompted by glucose intake, especially during post-prandial hyperglycaemic peaks. Mutations affecting this gene have been shown to exert a dominant-negative inhibition of the insulin gene transcription. A variety of oral anti-hyperglycaemic drugs have been suggested as therapeutical approaches, including metformin, DPP-4 inhibitors and sulfonylureas, which have proven their effectiveness in some case reports. The patient is a young lady referred to the Diabetes Unit after a recent diagnosis of diabetes mellitus, with glycosylated hemoglobin levels far above the reference range (HbA1c 117,5 mmol/mol, 12.95%) and strong familiarity in her descent (mother, father, and her brother). Her GP already prescribed her 500 mg of metformin three times per day. After the diabetology consultation, the patient was given 12,5 mg of empagliflozin (SGLT-2i) in addition to her previous therapeutical scheme. The genetic analysis showed an intragenic heterozygous variant mutation of uncertain significance of PDX1 gene, c.670G>A p.(Glu224Lys); this mutation has been previously reported in few cases and all diabetic relatives of our patient had thereafter been tested for such variant genic defect (test results are still in processing). After six months, glycosylated haemoglobin levels resulted greatly improved thanks to association therapy (HbA1c 61 mmol/mol, 7.7%). Our patient showed a very rare intragenic mutation of PDX1, responsible for MODY onset. Empagliflozin successfully helped to reduce glycaemic levels: the impaired encoded PDX1 protein is a transcriptional activator of glucose transporter type 2 (GLUT2), explaining the pharmacological rationale for the administration of SGLT2 inhibitors. In conclusion, SGLT2i could represent a useful therapeutical option in MODY-4 patients, independently from its association with metformin.