Leydig cell hypoplasia type 1 diagnosed in early childhood with inactivating mutation in LHCGR gene

ABSTRACT Leydig cell aplasia/hypoplasia is an autosomal recessive condition. In its complete form, these patients are 46XY but are cryptorchid and phenotypically female. Most cases reported in literature presented with in adolescence with pubertal delay. We reported a case with a predefined mutation in the LHCGR gene, presenting with swelling in the inguinal region and therefore diagnosed in early childhood. We wanted to emphasize the necessity of keeping Leydig cell hypoplasia in mind in the differential diagnosis of sexual development disorders in early childhood.

LEYDIG CELL HYPOPLASIA: A UNIQUE PARADOX IN THE DIAGNOSIS OF 46,XY DISORDERS OF SEX DEVELOPMENT

Objective: Disorders of sex development (DSD) are defined as conditions in which chromosomal sex is inconsistent with phenotypic sex, or in which the phenotype is not classifiable as either male or female. Mutations in genes present in X, Y or autosomal chromosomes can cause abnormalities of testis determination or 46,XY DSD. Leydig cell hypoplasia (LCH), also known as Leydig cell agenesis, is a rare autosomal recessive endocrine syndrome of 46,XY DSD. Our objective here is to present the case of a 27-year-old, phenotypic female who presented with primary amenorrhea and later found to have LCH. Methods: We used formatted history and clinical examination followed by necessary hormonal investigations. The diagnosis was confirmed by histopathology of resected testes and genetic mutation analysis. Results: The patient's physical examination was unremarkable except 2 ovoid lumps present in the inguinovulvar region. There were no müllerian structures on sonography. Estrogen and both basal and stimulated testosterone levels were low whereas luteinizing hormone and follicle-stimulating hormone were high. Her chromosomal sex was found to be 46,XY. The histopathology of the resected inguinal lumps showed atrophic testicular change lacking Leydig cells with relative preservation of Sertoli cells. Genetic mutation analysis failed to reveal any significant aberration in the LHCGR gene. At present she is on estrogen replacement therapy having undergone bilateral orchidectomy and vaginoplasty. Conclusion: LCH represents a unique example of diagnostic dilemma in gender identification. It requires a multidisciplinary approach for optimum outcome.

Novel compound heterozygous variants in the LHCGR gene identified in a subject with Leydig cell hypoplasia type 1

Background: Leydig cell hypoplasia (LCH) is a rare disease and one of the causes of male disorder of sexual differentiation (DSD). Inactivating mutations in the luteinizing hormone/chorionic gonadotropin receptor (LHCGR) gene account for the underlying LCH pathogenicity. This study aimed to analyze the clinical presentation and diagnosis as well as highlight the molecular characteristics of a subject with LCH type 1. Case presentation: Clinical data were collected from the subject and analyzed. Next generation sequencing of the immediate family pedigree using peripheral blood genomic DNA was performed, and the relevant mutations were verified with Sanger sequencing. We describe the case of a 5-year-old patient with DSD, presenting with a lateral inguinal hernia accompanied by abnormal hormone tests. The genetic analysis revealed novel compound heterozygous variants in the LHCGR gene, including a splice site mutation (c.681-1 G>A) and a frameshift variant (c.1582_1585del ATAT, p.Ile528*). Conclusions: We identified novel compound heterozygous variants in the LHCGR gene, and expanded the genotype-phenotype correlation spectrum of LHCGR variants.

Misfolding Ectodomain Mutations of the Lutropin Receptor Increase Efficacy of Hormone Stimulation

We demonstrate 2 novel mutations of the LHCGR, each homozygous, in a 46,XY patient with severe Leydig cell hypoplasia. One is a mutation in the signal peptide (p.Gln18_Leu19ins9; referred to here as SP) that results in an alteration of the coding sequence of the N terminus of the mature mutant receptor. The other mutation (p.G71R) is also within the ectodomain. Similar to many other inactivating mutations, the cell surface expression of recombinant human LHR(SP,G71R) is greatly reduced due to intracellular retention. However, we made the unusual discovery that the intrinsic efficacy for agonist-stimulated cAMP in the reduced numbers of receptors on the cell surface was greatly increased relative to the same low number of cell surface wild-type receptor. Remarkably, this appears to be a general attribute of misfolding mutations in the ectodomains, but not serpentine domains, of the gonadotropin receptors. These findings suggest that there must be a common, shared mechanism by which disparate mutations in the ectodomain that cause misfolding and therefore reduced cell surface expression concomitantly confer increased agonist efficacy to those receptor mutants on the cell surface. Our data further suggest that, due to their increased agonist efficacy, extremely small changes in cell surface expression of misfolded ectodomain mutants cause larger than expected alterations in the cellular response to agonist. Therefore, for inactivating LHCGR mutations causing ectodomain misfolding, the numbers of cell surface mutant receptors on fetal Leydig cells of 46,XY individuals exert a more exquisite effect on the relative severity of the clinical phenotypes than already appreciated.

A novel inactivating mutation of the LH/chorionic gonadotrophin receptor with impaired membrane trafficking leading to Leydig cell hypoplasia type 1

ObjectiveThe LH/chorionic gonadotrophin receptor (LHCGR) is a G protein-coupled receptor (GPCR) that plays a central role in male sexual differentiation, regulation of ovarian follicular maturation, ovulation and maintenance of corpus luteum and pregnancy, as well as maintenance of testicular testosterone production. Mutations in theLHCGRgene are very rare. The aim of this work was to study the clinical and molecular characteristics of a rare familialLHCGRmutation.MethodsFive affected members of a family, including a phenotypically female, but genotypically male (46,XY), patient with Leydig cell hypoplasia type 1 and four genotypically female siblings with reproductive abnormalities, were studied genetically. Cell trafficking studies as well as signalling studies of mutated receptor were performed.ResultsThe five affected patients were all homozygous for a novel mutation in theLHCGRgene, a deletion of guanine in position 1850 (1850delG). This resulted in a frameshift affecting most of the C-terminal intracellular domain.In vitrostudies demonstrated that the 1850delG receptor was completely incapable of transit to the cell membrane, becoming trapped within the endoplasmic reticulum. This could not be rescued by small-molecule agonist treatment or stimulated intracellularly by co-expression of a yoked human chorionic gonadotrophin.ConclusionsThis novelLHCGRmutation leads to complete inactivation of the LHCGR receptor due to trafficking and signalling abnormalities, which improves our understanding of the impact of the affected structural domain on receptor trafficking and function.