Insulin resistant diabetes mellitus in a girl with mild Rabson-Mendenhall syndrome: efficacy of sodium glucose co-transporter 2 inhibitor.

We report a beneficial effect of a sodium glucose co-transporter 2 (SGLT2) inhibitor in the management of insulin resistant diabetes mellitus (IRDM) in a Japanese girl with mild Rabson-Mendenhall syndrome (RMS). At 10 2/12 years of age, she was referred to us because of glucosuria, and was found to have marked acanthosis nigricans and RMS-like facial features such as proptosis, large ears, full lips, and gingival hypertrophy, but not other clinical features frequently found in RMS. At 11 9/12 years of age, her blood HbA1c level, though it remained ~ 6.5% until then, increased to 7.9% with pubertal development. She was treated with an SGLT2 inhibitor and metformin, which ameliorated overt hyperglycemia in the afternoon and the evening (postprandial time) as well as obvious hypoglycemia in the early morning (before breakfast), and reduced her blood HbA1c to 5.5%. Whole exome sequencing revealed probably disease-causing c.2465 T > C:p.(Leu822Pro) of paternal origin and c.3038C > T:p.(Pro1013Leu) of maternal origin in INSR. These findings imply the usefulness of SGLT2 inhibitor in the treatment of IRDM. It is likely that SGLT2 inhibitor mitigated hyperglycemia by increasing the urine glucose excretion and prevented severe hypoglycemia probably because of attenuated hyperinsulinemia in the absence of overt hyperglycemia.