Hypoglycaemia revealing heterozygous insulin receptor mutations.

Abstract : Major hyperinsulinemia, acanthosis nigricans, impaired glucose tolerance and ovarian hyperandrogenism characterize Type A insulin resistance (IR) syndrome due to dominant-negative heterozygous mutations in the insulin receptor gene (INSR). However, two unrelated families have been described with symptomatic hypoglycemia due to heterozygous INSR p.Arg1201 substitutions in the tyrosine kinase domain. In these patients, major hyperinsulinemia together with decreased insulin clearance was suggested to rescue genetically-altered insulin signalling in vivo in liver and/or muscle. We broaden the genetic spectrum of this rare phenotype of Type A insulin resistance by reporting the observations of two patients with INSR p.Met1180Val or p.Arg1201Gln heterozygous mutations revealed by repeated symptomatic hypoglycemia. Our observations further demonstrate that hyperinsulinemic hypoglycemia in adults can reveal different heterozygous mutations in the insulin receptor tyrosine kinase domain, whether associated or not with acanthosis nigricans, impaired glucose tolerance and/or ovarian hyperandrogenism.