Type A insulin resistance syndrome due to a novel heterozygous c.3486_3503del (p.Arg1163_ Ala1168del) INSR gene mutation in an adolescent girl and her mother

Abstract

Mutations in the insulin receptor (INSR) gene may present with variable clinical phenotypes. We report herein a novel heterozygous INSR mutation in an adolescent girl with type A insulin resistance syndrome and her mother.The index case was a 12-year-old girl without obesity who presented with excessive hair growth, especially in the chest and back area, and hyperpigmentation on the back of the neck (acanthosis nigricans). Acanthosis nigricans was first observed at the age of 11 years. On physical examination, the patient had acanthosis nigricans and hypertrichosis with no acne. Systolic and diastolic blood pressure measurement was within the normal range for age and sex. Laboratory tests revealed fasting hyperglycemia, fasting and postprandial hyperinsulinemia, elevated HbA1c level, and biochemical hyperandrogenemia. Fasting plasma lipids were normal. A diagnosis of type A insulin resistance syndrome was considered, and INSR gene mutation analysis was performed. Nextgeneration sequence analysis was performed with the use of primers containing exon/exon-intron junctions in the INSR gene, and a novel heterozygous c.3486_3503delGAGAAACTGCATGGTCGC/p. Arg1163_Ala1168del change was detected in exon 19 of the INSR gene. In segregation analysis, the same variant was detected in the patient's mother, who had a milder clinical phenotype.We reported a novel, heterozygous, p.Arg1163_Ala1168del mutation in exon 19 of the INSR gene in a patient with type A insulin resistance syndrome, expanding the mutation database. The same mutation was associated with variable phenotypical severity in two subjects within the same family.