Non-invasive diagnosis and follow-up of hyperferritinaemia

International audienc

Variable expressivity of HJV related hemochromatosis: “Juvenile” hemochromatosis?

International audienceJuvenile hemochromatosis is a rare autosomal recessive disease due to variants in the Hemojuvelin (HJV) gene. Although biological features mimic HFE hemochromatosis, clinical presentation is worst with massive iron overload diagnosed during childhood.Our study describes clinical features and results of genetic testing for a group of patients initially referred for a hepcidino-deficiency syndrome and for whom HJV hemochromatosis was finally diagnosed. 662 patients with iron overload and high serum transferrin saturation were tested, and five genes (HFE, HJV, HAMP, TFR2, SLC40A1) were sequenced.Among our cohort, ten unrelated patients were diagnosed with HJV hemochromatosis. Genetic testing revealed five previously published and five undescribed variants: p.Arg41Pro, p.His180Arg, p.Lys299Glu, p.Cys361Arg and p.Ala384Val.Surprisingly, this study revealed a late age of onset in some patients, contrasting with the commonly accepted definition of “juvenile” hemochromatosis. Five of our patients were 30 years old or older, including two very late discoveries. Biological features and severity of iron overload were similar in younger and older patients.Our study brings new insight on HJV hemochromatosis showing that mild phenotype and late onset are possible. Genetic testing for HJV variants should thus be performed for all patients displaying a non-p.Cys282Tyr homozygous HFE hemochromatosis with hepcidin deficiency phenotype

Targeted panel sequencing establishes the implication of planar cell polarity pathway and involves new candidate genes in neural tube defect disorders

International audienceNeural tube defect disorders are developmental diseases that originate from an incomplete closure of the neural tube during embryogenesis. Despite high prevalence-1 out of 3000 live births-their etiology is not yet established and both environmental and genetic factors have been proposed, with a heritability rate of about 60%. Studies in mouse models as well as in human have further suggested a multifactorial pattern of inheritance for neural tube defect disorders. Here, we report results obtained from clinical diagnosis and NGS analysis of a cohort composed of 52 patients. Using a candidate gene panel approach, we identified variants in known genes of planar cell polarity (PCP) pathway, although with higher prevalence than previously reported. Our study also reveals variants in novel genes such as FREM2 and DISP1. Altogether, these results confirm the implication of the PCP genes and involve the FRAS/FREM2 complex and Sonic Hedgehog signaling as novel components in the appearance of NTDs

Disrupted hypothalamo-pituitary axis in association with reduced SHH underlies the pathogenesis of NOTCH-deficiency

International audienceContext: In human, Sonic Hedgehog, SHH, haploinsufficiency is the predominant cause of holoprosencephaly, a structural malformation of the forebrain midline characterised by phenotypic heterogeneity and incomplete penetrance. The NOTCH signalling pathway has recently been associated with holoprosencephaly, in humans, but the precise mechanism involving NOTCH signalling during early brain development remains unknown.Objective: The aim of this study was to evaluate the relationship between SHH and NOTCH signalling in order to determine the mechanism by which NOTCH dysfunction could cause midline malformations of the forebrain.Design: In this study, we have used a chemical inhibition approach in the chick model and a genetic approach in the mouse model. We reported results obtained from clinical diagnosis of a cohort composed of 141 holoprosencephaly patients.Results: We demonstrated that inhibition of NOTCH signalling in chick embryos as well as in mouse embryos induces a specific downregulation of SHH in the anterior hypothalamus. Our data in the mouse also revealed that the pituitary gland was the most sensitive tissue to Shh insufficiency and that haploinsufficiency of the SHH and NOTCH signalling pathways synergized to produce a malformed pituitary gland. Analysis of a large holoprosencephaly cohort revealed that some patients possessed multiple heterozygous mutations in several regulators of both pathways.Conclusions: These results provided new insights into molecular mechanisms underlying the extreme phenotypic variability observed in human holoprosencephaly. They showed how haploinsufficiency of the SHH and NOTCH activity could contribute to specific congenital hypopituitarism that was associated with a sella turcica defect

Oligogenic inheritance in neural tube defects: major involvment of primary cilia, planar cell polarity and extracellular matrix genes

International audienc

A simple clinical and biological score to promote and enhance Ferroportine disease screening.

International audienc

A simple clinical score to promote and enhance ferroportin disease screening

International audienceBackground & aims - Ferroportin disease is a rare genetic iron overload disorder which may be underdiagnosed, with recent data suggesting it occurs at a higher prevalence than suspected. Costs and the lack of defined criteria to prompt genetic testing preclude large-scale molecular screening. Hence, we aimed to develop a readily available scoring system to promote and enhance ferroportin disease screening. Methods - Our derivation cohort included probands tested for ferroportin disease from 2008 to 2016 in our rare disease network. Data were prospectively recorded. Univariate and multivariate logistic regression were used to determine significant criteria, and odds ratios were used to build a weighted score. A cut-off value was defined using a ROC curve with a predefined aim of 90% sensitivity. An independent cohort was used for cross validation. Results - Our derivation cohort included 1,306 patients. Mean age was 55±14 years, ferritin 1,351±1,357 μg/L, and liver iron concentration (LIC) 166±77 μmol/g. Pathogenic variants (n = 32) were identified in 71 patients. In multivariate analysis: female sex, younger age, higher ferritin, higher LIC and the absence of hypertension or diabetes were significantly associated with the diagnosis of ferroportin disease (AUROC in whole derivation cohort 0.83 [0.78-0.88]). The weighted score was based on sex, age, the presence of hypertension or diabetes, ferritin level and LIC. An AUROC of 0.83 (0.77-0.88) was obtained in the derivation cohort without missing values. Using 9.5 as a cut-off, sensitivity was 93.6 (91.7-98.3) %, specificity 49.5 (45.5-53.6) %, positive likelihood ratio 1.8 (1.6-2.0) and negative likelihood ratio 0.17 (0.04-0.37). Conclusion - We describe a readily available score with simple criteria and good diagnostic performance that could be used to screen patients for ferroportin disease in routine clinical practice. Lay summary - Increased iron burden associated with metabolic syndrome is a very common condition. Ferroportin disease is a dominant genetic iron overload disorder whose prevalence is higher than initially thought. They can be difficult to distinguish from each other, but the limited availability of genetic testing and the lack of definitive guidelines prevent adequate screening. We herein describe a simple and definitive clinical score to help clinicians decide whether to perform genetic testing