Glimepiride treatment in a patient with type A insulin resistance syndrome due to a novel heterozygous missense mutation in the insulin receptor gene

AIMS/INTRODUCTION: Glimepiride is a sulfonylurea known to have unique insulin mimetic and sensitizing effects. We aimed to study the efficacy of glimepiride in a patient with type A insulin resistance syndrome. MATERIALS AND METHODS: A 15‐year‐old girl with type A insulin resistance syndrome was treated with glimpiride for 6 months. Self‐monitoring of blood glucose was recorded, and oral glucose tolerance tests on glucose and insulin were measured during the treatment. Hyperinsulinemic euglycemic clamp was used to evaluate whole‐body insulin sensitivity before and after the treatment. RESULTS: A novel heterozygous missense mutation at exon 19 (c.3427A>T) in the tyrosine kinase domain of the INSR gene was identified, causing an amino acid replacement of phenylalanine for isoleucine at codon 1143 (Ile1143Phe). Before the treatment, the patient's glycated hemoglobin was 7.0%, plasma glucose during oral glucose tolerance test was 6.7, 12.8 and 17.3 mmol/L, and simultaneous serum insulin was 80.7, 137.5 and >300 μU/mL. There were no significant differences between self‐monitored blood glucose measured at each time‐point among different glimepiride dosages, or during the 14 weeks when glimepiride was used at its maximal dosage (6 mg/day). Oral glucose tolerance test showed little change in plasma glucose and serum insulin. Glycated hemoglobin decreased by 0.8% after the treatment. However, a euglycemic clamp study showed that the M value decreased from 5.25 to 2.90 mg/kg/min, showing increased insulin resistance. CONCLUSIONS: Treatment with glimepiride did not improve insulin sensitivity in a patient with type A insulin resistance syndrome carrying Ile1143Phe heterozygous mutation in the INSR gene. Large‐scale long‐term studies assembled worldwide are required to optimize treatment algorithms for patients with type A insulin resistance syndrome.