A case of type A insulin resistance syndrome in a 14-year-old adolescent girl without common clinical features.

Abstract

Type A insulin resistance syndrome is a rare congenital disorder caused by insulin receptor dysfunction arising from heterozygous mutations in the insulin receptor (INSR) gene. It is usually diagnosed in non-obese female adolescents with insulin resistance, acanthosis nigricans, or ovarian hyperandrogenism. We present the case of a 14-year-old adolescent girl with non-obesity diabetes and insulin resistance; however, she had no acanthosis nigricans, or menstrual abnormalities. The laboratory results were as follows: fasting plasma glucose 179 mg/dL; C-peptide 1.8 ng/mL; insulin 34.8 lU/mL; HbA1c 10.6%. Islet cell autoantibodies, insulin autoantibodies, and glutamic acid decarboxylase antibodies were negative. We performed a next-generation sequencing-based targeted gene panel for the known maturity-onset diabetes of the young and found a heterozygous mutation in the INSR gene c.3602G>A (p.Arg1201Gln). Her mother carried the same mutation as her and also did not present with acanthosis nigricans or menstruation abnormalities. Type A insulin resistance syndrome has diverse clinical phenotypes even with the same type of mutation at the same site in the INSR gene. Clinicians should consider genetic testing for early detection and adequate treatment approaches.