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Homozygous Mutation in the Insulin Receptor Gene Associated with Mild Type A Insulin Resistance Syndrome: A Case Report

ABSTRACT: Insulin receptor (INSR) mutations lead to heterogeneous disorders that may be as severe as Donohue syndrome or as mild as “type A insulin resistance syndrome”. Patients with severe disorders usually harbor homozygous or compound heterozygous mutations. In contrast, type A insulin resistance syndrome has been associated with heterozygous mutations; homozygous mutations are rarely responsible for this condition. We report a novel, homozygous mutation, p.Leu260Arg in exon 3, of the INSR gene in a female adolescent patient with type A insulin resistance syndrome together with clinical details of her medical follow-up. Different mutations in the INSR gene cause different phenotype and vary depending on the inheritance pattern. This report adds to the literature, increases understanding of the disease mechanism and aids in genetic counseling.

SUBMITTER: Hacıhamdioglu B

PROVIDER: S-EPMC7947722 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Homozygous Mutation in the Insulin Receptor Gene Associated with Mild Type A Insulin Resistance Syndrome: A Case Report

Hacıhamdioğlu Bülent B Baş Elif Gülşah EG Delil Kenan K

Journal of clinical research in pediatric endocrinology 20200205 1

Insulin receptor (INSR) mutations lead to heterogeneous disorders that may be as severe as Donohue syndrome or as mild as “type A insulin resistance syndrome”. Patients with severe disorders usually harbor homozygous or compound heterozygous mutations. In contrast, type A insulin resistance syndrome has been associated with heterozygous mutations; homozygous mutations are rarely responsible for this condition. We report a novel, homozygous mutation, p.Leu260Arg in exon 3, of the <i>INSR</i> gene ...[more]

PMID: 32018348

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Project description:BACKGROUND:4H syndrome is a congenital hypomyelinating leukodystrophy characterized by hypodontia, hypomyelination and hypogonadotropic hypogonadism belonging to the Pol III-related leukodystrophies which arise due to mutations in the POLR3A or POLR3B gene. The clinical presentation is of neurodevelopmental delay or regression with ataxia, dystonia, nystagmus, delayed deciduous dentition and abnormal order of eruption of teeth. MRI brain shows a characteristic hypomyelination pattern. Several mutations have been described in the implicated genes but there are no reports on mutations seen in patients from India. CASE PRESENTATION:We report a 1½ year old girl, only child of a non-consanguinous couple who presented with delayed developmental milestones and delayed dentition. On physical examination she had downward slanting palpebral fissures, low set ears, smooth philtrum, hypodontia, prominent body hair and clitoromegaly. There was prominent horizontal nystagmus, hypertonia of both upper and lower limbs, exaggerated deep tendon jerks and flexor planter response. She had not attained complete head control and required support to sit. She showed absent waves on brainstem evoked response audiometry and her fundus examination showed bilateral optic atrophy with prolongation of P100 latencies on visual evoked potentials. MRI Brain showed hyperintensity of entire white matter with involvement of the internal and external capsule, frontal deep white matter and corpus callosum. Her karyotype was 46 XX and her endocrinal profile was unremarkable. Clinical exome sequencing identified an unreported mutation in the POLR3A gene. The same mutation was identified by Sanger sequencing in heterozygous state in both parents. The child is being managed with physiotherapy and developmental therapy. She has been provided with hearing aids and started on speech therapy. Parents were provided anticipatory guidance and genetic counselling about autosomal recessive nature of inheritance, risk of recurrence and need for follow-up. CONCLUSION:4H syndrome is a rare congenital hypomyelinating leukodystrophy inherited as an autosomal recessive disorder due to mutations in the POLR3A and POLR3B gene. Delay or regression of milestones, abnormalities in dentition and endocrinal perturbations are its hallmark. A novel mutation in the POLR3A gene resulting in amino acid substitution of arginine for glutamine at codon 808 (p.R808Q) was detected in exon 18 in our case.

Project description:BackgroundGlucocorticoid resistance is a rare, sporadic or familial condition caused by mutation of the gene encoding the glucocorticoid receptor (GR). Clinically it is characterized by symptoms developed due to local, tissue-specific, or generalized partial insensitivity to glucocorticoids.Case presentationA 31-year-old woman was evaluated because of infertility at the Endocrine Unit of the 2nd Department of Medicine, Semmelweis University. During her laboratory investigations, elevated serum and salivary cortisol were observed which failed to be suppressed after administration of 1 mg dexamethasone. 24 h urinary cortisol was increased, but a normal midnight serum cortisol was detected suggesting a maintained circadian rhythm. Plasma dehydroepiandrosterone-sulfate and androstendione levels were also elevated. Repeated plasma ACTH measurements indicated slightly elevated or normal values. Bone mineral density was normal. All laboratory results confirmed the diagnosis of glucocorticoid resistance. Genetic counseling followed by Sanger sequencing of the coding region of the gene encoding human glucocorticoid receptor was performed and a missense mutation (Arg714Gln, R714Q) in a heterozygous form was detected. Following family screening, the same mutation was found in her clinically-healthy 35-year-old sister who had no fertility problems.This variant was not detected in more than 60 patients and controls tested either for glucocorticoid resistance or Cushing's syndrome in our Laboratory and it was absent in Exome Variant Server, HumanGene Mutation Database and ExAC databases.ConclusionsOur case fulfils the diagnostic criteria of glucocorticoid resistance, also named Chrousos syndrome. The glucocorticoid receptor gene mutation detected in our patient has been already reported in a 2-year-old child with hypoglycaemia, hypokalaemia, hypertension and premature puberty. These distinct phenotypes may suggest that other factors may modify the functional consequences of the R714Q variant of GR.

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Homozygous Mutation in the Insulin Receptor Gene Associated with Mild Type A Insulin Resistance Syndrome: A Case Report

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Homozygous Mutation in the Insulin Receptor Gene Associated with Mild Type A Insulin Resistance Syndrome: A Case Report

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