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Background Participation in quality controls, also called external quality assessment (EQA) schemes, is required for the ISO15189 accreditation of the Medical Centers of Human Genetics. However, directives on the minimal frequency of participation in genetic quality control schemes are lacking or too heterogeneous, with a possible impact on health care quality. Objective The aim of this project is to develop Belgian guidelines on the frequency of participation in quality controls for genetic testing in the context of rare diseases. Methods A group of experts analyzed 90 EQA schemes offered by accredited providers and focused on analyses used for the diagnosis of rare diseases. On that basis, the experts developed practical recommendations about the minimal frequencies of participation of the Medical Centers of Human Genetics in quality controls and how to deal with poor performances and change management. These guidelines were submitted to the Belgian Accreditation Body and then reviewed and approved by the Belgian College of Human Genetics and Rare Diseases and by the National Institute for Health and Disability Insurance. Results The guidelines offer a decisional algorithm for the minimal frequency of participation in human genetics EQA schemes. This algorithm has been developed taking into account the scopes of the EQA schemes, the levels of experience, and the annual volumes of the Centers of Human Genetics in the performance of the tests considered. They include three key principles: (1) the recommended annual assessment of all genetic techniques and technological platforms, if possible through EQAs covering the technique, genotyping, and clinical interpretation; (2) the triennial assessment of the genotyping and interpretation of specific germline mutations and pharmacogenomics analyses; and (3) the documentation of actions undertaken in the case of poor performances and the participation to quality control the following year. The use of a Bayesian statistical model has been proposed to help the Centers of Human Genetics to determine the theoretical number of tests that should be annually performed to achieve a certain threshold of performance (eg, a maximal error rate of 1%). Besides, the guidelines insist on the role and responsibility of the national public health authorities in the follow-up of the quality of analyses performed by the Medical Centers of Human Genetics and in demonstrating the cost-effectiveness and rationalization of participation frequency in these quality controls. Conclusions These guidelines have been developed based on the analysis of a large panel of EQA schemes and data collected from the Belgian Medical Centers of Human Genetics. They are applicable to other countries and will facilitate and improve the quality management and financing systems of the Medical Centers of Human Genetics.

BACKGROUND Participation in quality controls, also called external quality assessment (EQA) schemes, is required for the ISO15189 accreditation of the Medical Centers of Human Genetics. However, directives on the minimal frequency of participation in genetic quality control schemes are lacking or too heterogeneous, with a possible impact on health care quality. OBJECTIVE The aim of this project is to develop Belgian guidelines on the frequency of participation in quality controls for genetic testing in the context of rare diseases. METHODS A group of experts analyzed 90 EQA schemes offered by accredited providers and focused on analyses used for the diagnosis of rare diseases. On that basis, the experts developed practical recommendations about the minimal frequencies of participation of the Medical Centers of Human Genetics in quality controls and how to deal with poor performances and change management. These guidelines were submitted to the Belgian Accreditation Body and then reviewed and approved by the Belgian College of Human Genetics and Rare Diseases and by the National Institute for Health and Disability Insurance. RESULTS The guidelines offer a decisional algorithm for the minimal frequency of participation in human genetics EQA schemes. This algorithm has been developed taking into account the scopes of the EQA schemes, the levels of experience, and the annual volumes of the Centers of Human Genetics in the performance of the tests considered. They include three key principles: (1) the recommended annual assessment of all genetic techniques and technological platforms, if possible through EQAs covering the technique, genotyping, and clinical interpretation; (2) the triennial assessment of the genotyping and interpretation of specific germline mutations and pharmacogenomics analyses; and (3) the documentation of actions undertaken in the case of poor performances and the participation to quality control the following year. The use of a Bayesian statistical model has been proposed to help the Centers of Human Genetics to determine the theoretical number of tests that should be annually performed to achieve a certain threshold of performance (eg, a maximal error rate of 1%). Besides, the guidelines insist on the role and responsibility of the national public health authorities in the follow-up of the quality of analyses performed by the Medical Centers of Human Genetics and in demonstrating the cost-effectiveness and rationalization of participation frequency in these quality controls. CONCLUSIONS These guidelines have been developed based on the analysis of a large panel of EQA schemes and data collected from the Belgian Medical Centers of Human Genetics. They are applicable to other countries and will facilitate and improve the quality management and financing systems of the Medical Centers of Human Genetics.

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.

Congenital hypothyroidism (CH) is a relatively frequent and potentially severe disease. It is classically subdivided into: 1) thyroid dysgenesis (TD), a defect in the organogenesis of the gland leading to hypoplastic, ectopic, or absent thyroid gland; or 2) thyroid dyshormonogenesis, a defect in one of the biochemical mechanisms responsible for thyroid hormone synthesis. Most cases of TD are sporadic, although familial occurrences have occasionally been described. Recently, several genes have been implicated in a small proportion of TD, but, in the majority of the cases, the etiology remains unknown. PAX8 is a transcription factor involved in thyroid development. So far, three loss-of-function mutations of PAX8 have been described, two in sporadic cases and one in familial thyroid hypoplasia. Here, we describe a novel mutation of PAX8 causing autosomal dominant transmission of CH with thyroid hypoplasia. The mutation consists of the substitution of a tyrosine for cysteine 57 in the paired domain of PAX8. When tested in cotransfection experiments with a thyroid peroxidasse promoter construct, the mutant allele was unable to exert its normal transactivation effect on transcription. Our results give further evidence that, contrary to the situation in knockout mice, haplo-insufficiency of PAX8 is a cause of CH in humans.

ObjectiveGenetic disorders of calcium metabolism arise in a familial or sporadic setting. The calcium-sensing receptor (CASR) plays a key role in maintaining calcium homeostasis and study of theCASRgene can be clinically useful in determining etiology and appropriate therapeutic approaches. We report two cases of novelCASRgene mutations that illustrate the varying clinical presentations and discuss these in terms of the current understanding of CASR function.Patients and methodsA 16-year-old patient had mild hypercalcemia associated with low-normal urinary calcium excretion and normal-to-high parathyroid hormone (PTH) levels. Because of negative family history, familial hypocalciuric hypercalcemia was originally excluded. The second patient was a 54-year-old man with symptomatic hypocalcemia, hyperphosphatemia, low PTH, and mild hypercalciuria. Familial investigation revealed the same phenotype in the patient's sister. The coding region of theCASRgene was sequenced in both probands and their available first-degree relatives.ResultsThe first patient had a novel heterozygous inactivatingCASRmutation in exon 4, which predicted a p.A423K change; genetic analysis was negative in the parents. The second patient had a novel heterozygous activatingCASRmutation in exon 6, which predicted a p.E556K change; the affected sister of the proband was also positive.ConclusionsWe reported two novel heterozygous mutations of theCASRgene, an inactivating mutation in exon 4 and the first activating mutation reported to date in exon 6. These cases illustrate the importance of genetic testing ofCASRgene to aid correct diagnosis and to assist in clinical management.

Endocrinology Service and Research Center (S.S.-V., J.D.), Otorhinolaryngology Department (A.L.), and Nuclear Medicine Service (S.T.), Centre Hospitalier Universitaire Sainte-Justine, Department of Pediatrics, University of Montreal, Montreal, Canada H3T 1C5; and Institut de Recherche Interdisciplinaire en Biologie Humaine et Moleculaire and Genetics Service (C.R., G.V.), Erasme Hospital, Free University of Brussels, B-1070 Brussels, Belgium

CONTEXT: Resistance to TSH (RTSH) is an inherited disorder of variable hyposensitivity to TSH. The metabolic consequences can range from euthyroid hyperthyrotropinemia to severe congenital hypothyroidism with thyroid hypoplasia. Although subclinical and mild hypothyroidism fitting the RTSH phenotype is common in the population, the role of genetic factors is far from being understood. Only in rare cases has RTSH been attributed to TSHR or PAX8 gene mutations. OBJECTIVE, SETTING, AND PARTICIPANTS: Toward the identification of novel RTSH genes, we studied five large, unrelated families comprising 102 individuals, 56 of whom were affected. RESULTS: Inheritance of RTSH in these families followed an autosomal dominant pattern without evidence for incomplete penetrance, yet expressivity was variable. Considering only fully phenotyped generations, 64% of the progeny was affected, with a 1:1.4 male-to-female ratio. Of 18 affected individuals tested in the neonatal period, two were undetected because of borderline results. The thyroid phenotype was indistinguishable from that observed with PAX8 and TSHR defects. In four families, untreated affected subjects of all ages had elevated serum thyroglobulin levels, consistent with a defect in the thyroid follicle cells. Linkage of RTSH to TSHR and PAX8 was excluded in all five families. For the largest families, we likewise excluded a contribution of genes previously only associated with syndromic forms of RTSH, namely TITF1, GNAS, and FOXE1. CONCLUSIONS: These kindreds represent a distinct etiological entity of autosomal dominant RTSH. According to the clinical presentation of these families, genetic causes of mild hyperthyrotropinemia in the general population may be more common than currently appreciated.

Thyroid dysgenesis is the most common cause of congenital hypothyroidism, a relatively frequent disease affecting 1 in 3000–4000 newborns. Whereas most cases are sporadic, mutations in transcription factors implicated in thyroid development have been shown to cause a minority of cases transmitted as monogenic Mendelian diseases. PAX8 is one of these transcription factors, and so far, five mutations have been identified in its paired domain in patients with thyroid dysgenesis. We have identified a novel mutation of PAX8, in the heterozygous state, in a father and his two children both presenting with congenital hypothyroidism associated with an in-place thyroid of normal size at birth. In addition, one of the affected siblings displayed unilateral kidney agenesis. The mutation substitutes a highly conserved serine in position 54 of the DNA-binding domain of the protein (S54G mutation) by a glycine. Functional analyses of the mutant protein (PAX8-S54G) demonstrated that it is unable to bind a specific cis-element of the thyroperoxidase gene promoter in EMSAs and that it has almost completely lost the ability to act in synergy with Titf1 to transactivate transcription from the thyroglobulin promoter/enhancer. These results indicate that loss of function mutations of the PAX8 gene may cause congenital hypothyroidism in the absence of thyroid hypoplasia.