• Lu Yu, Fang Yu, Zongrui Ma, Huilin Lu, Jian Luo, Ting Sun, Qin Liu, and Shenglian Gan.
• Department of Endocrinology and Metabolism, The First People's Hospital of Changde City, Changde, Hunan, P. R. China.
• Medicine (Baltimore). 2022 Dec 9; 101 (49): e32266e32266.

RationaleSevere insulin receptor gene (INSR)-related insulin resistance syndromes (SIR) include Donohue syndrome (DS), Rabson-Mendenhall syndrome (RMS), and type A insulin resistance. The incidence of DS is about 1 in 4 million births. We identified novel INSR mutations (c.2246delG and c.2646 + 5G > A) in a patient with SIR, which expanded the variant spectrum and helped to improve the understanding of the diagnosis and treatment of this condition.Patient ConcernsA 10-year-old Chinese boy was admitted to the hospital for deepening skin color. He presented with growth retardation, peculiar facial features, acanthosis nigricans, hypertrichosis, extremely high insulin levels, fasting hypoglycemia, and postprandial hyperglycemia, Whole-exome gene testing suggested compound heterozygous mutations in INSR (c.2246delG and c.2646 + 5G > A).DiagnosisThe diagnosis was SIR. What's more, based on the phenotypic and biographical results, this child did not present typical RMS and DS but rather an intermediate phenotype between the 2 conditions.InterventionsOn the basis of a sensible diet and exercise, the patient was prescribed metformin (250 mg) at breakfast and lunch, which was increased to 500 mg after 1 month.OutcomesAfter 2 months of treatment, the patient's glycated hemoglobin (HbA1c) levels decreased to 6% but his insulin resistance did not improve significantly.LessonsIn children who are not obese but with severe insulin resistance, growth retardation, hirsutism, and hyperglycemia, genetic testing should be performed for early diagnosis, active treatment, and follow-up.Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.

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