LBODP032 Case Report Of A 13 Years Old Female With A Novel Pathogenic Variant In The Hnf1b Gene

BACKGROUND: MODY5 results from mutations in the gene encoding hepatocyte nuclear factor 1 homeobox B (HNF1B), a transcription factor critical in development of the pancreas, liver, intestines, and the urogenital tract (1). We report the case of a pediatric patient with a novel frameshift variant (p. Phe309SerfsTer18) in the HNF1B gene accounting for the co-occurrence of diabetes mellitus and structural renal abnormalities. Clinical case: A 13-years-old female with chronic kidney disease stage 3 (eGFR = 48 ml/min/1.73m2) secondary to congenital dysplastic-appearing left kidney and surgical removal of a cystic dysplastic right kidney was referred to our diabetes clinic for hyperglycemia. She reported long-standing polyuria and polydipsia previously attributed to her kidney disease. She required laparoscopic right nephrectomy at age 5 years due to increasing cyst size. Her left kidney also has small renal parenchymal cysts which have been monitored over time. There is no known family history of kidney disease, and grandparents have a history of diabetes. Laboratory investigation revealed a random blood glucose of 478 mg/dL and a hemoglobin A1c of 12.2%. She was not in diabetic ketoacidosis. She had a detectable insulin level of 5.1 mcIU/mL and C-peptide was 3.4 ng/mL. She was initially presumed to have Type 1 diabetes based on a relatively low insulin level and started on basal-bolus insulin (up to 0.59 units/kg of weight/day). Glycosylated hemoglobin was 8.7% one month after diagnosis. Glutamic acid decarboxylase, zinc transporter, islet cell, and insulin autoantibodies were not detected, however, and she was then suspected to have either Type 2 diabetes or MODY. Approximately one year later, she was taken off insulin due to hypoglycemia and managed only with metformin 500 mg twice daily. Next-generation sequencing revealed a de novo pathogenic variant in HNF1B causing a frameshift deletion (p. Phe309SerfsTer18). Genetic testing of parents was negative. Once her diagnosis of MODY5 was made, she was started on glipizide 2.5 mg once daily which has been titrated up to a dose of 5 mg with some success. However, she has since been re-started on insulin (up to 0.2 units/kg/day) due to hyperglycemia keeping in line with the MODY5 phenotype likely causing destruction of beta cells over time (1). CONCLUSION: We report a case of MODY5 with a novel frameshift mutation (p. Phe309SerfsTer18) in the HNF1B gene. This case highlights the importance of screening for HNF-1B mutations in those patients with structural renal abnormalities and hyperglycemia, as diagnosis can guide management decisions and provide prognostic information. Reference Bellanné-Chantelot C, Chauveau D, Gautier JF, et al. Clinical spectrum associated with hepatocyte nuclear factor-1beta mutations. Ann Intern Med. 2004;140(7): 510-517. doi: 10.7326/0003-4819-140-7-200404060-0000 Presentation: No date and time listed