Noninvasive prenatal diagnosis of genetic diseases induced by triplet repeat expansion by linked read haplotyping and Bayesian approach.

The field of noninvasive prenatal diagnosis (NIPD) has undergone significant progress over the last decade. Direct haplotyping has been successfully applied for NIPD of few single-gene disorders. However, technical issues remain for triplet-repeat expansions. The objective of this study was to develop an NIPD approach for couples at risk of transmitting dynamic mutations. This method includes targeted enrichment for linked-read libraries and targeted maternal plasma DNA sequencing. We also developed an innovative Bayesian procedure to integrate the Hoobari fetal genotyping model for inferring the fetal haplotype and the targeted gene variant status. Our method of directly resolving parental haplotypes through targeted linked-read sequencing was smoothly performed using blood samples from families with Huntington's disease or myotonic dystrophy type 1. The Bayesian analysis of transmission of parental haplotypes allowed defining the genotype of five fetuses. The predicted variant status of four of these fetuses was in agreement with the invasive prenatal diagnosis findings. Conversely, no conclusive result was obtained for the NIPD of fragile X syndrome. Although improvements should be made to achieve clinically acceptable accuracy, our study shows that linked-read sequencing and parental haplotype phasing can be successfully used for NIPD of triplet-repeat expansion diseases.Trial registration: NCT04698551_date of first registration: 07/01/2021.

[Linear lesions: A key dermatological feature of X-linked ectodermal dysplasia in a young girl]. / Lésions linéaires : un signe dermatologique clé de la dysplasie ectodermique liée à l'X chez la fille.

INTRODUCTION: X-linked hypo/anhidrotic ectodermal dysplasia (AED) is the most common form of AED. It is manifested in boys by involvement of the adnexa, teeth and sweat glands. In girls, signs are usually minor and may include linear lesions that are poorly known since they are reported infrequently or overlooked. Herein we report 3 cases. PATIENTS AND METHODS: There were two female patients who had been followed for several years, as well as the mother of one of the patients. Both of the younger patients had early diagnosis of DEA in childhood based on severe dental abnormalities, i.e. hypodontia and conical teeth, a typical facies, and cutaneous xerosis. The mother had milder signs and the diagnosis was made at the time of her daughter's diagnosis. All 3 had hypopigmented linear skin lesions (arms, buttocks or back), associated with a decrease in hair in one of them. Genetic analysis showed the R156H missense mutation at exon 3 of the EDA gene in all 3 patients. CONCLUSION: These hypopigmentation linear lesions, sometimes with hair loss, are well known to pediatric clinicians and dermatologists concerning early diagnosis of AED in girls, especially where the other signs are mild. Early diagnosis enables appropriate therapeutic management and genetic counseling regarding future pregnancy.

[Clinical and evolutionary characteristics of a child with aquagenic keratoderma: A retrospective study of 12 patients]. / Caractéristiques cliniques et évolutives de la kératodermie aquagénique de l'enfant : étude rétrospective de 12 cas.

INTRODUCTION: Aquagenic keratoderma (AK) is a rare condition characterized by wrinkled and edematous appearance of the skin of the hands occurring within minutes of immersion in water. Other than in a setting of cystic fibrosis, AK has rarely been reported in children, with only 13 clinical cases on record. Many clinicians are unfamiliar with AK and have fears relating to the association with cystic fibrosis The aim of this study is to describe the characteristics and to discuss management of the disease. METHODS: Retrospective, multicentre study, including children aged under 16 years presenting AK. RESULTS: 12 children were included. KA started at a mean age of 9.25 years (range: 20 months to 15 years). Clinical appearance and mode of onset were classical, with the palms being more severely affected than the soles. Pruritus or pain were reported in six cases. The median impact on daily life was 1.5/10. Some of the children underwent investigations: two had a negative sweat test, three had molecular analysis of the gene CFTR: one was negative and two had a heterozygote mutation. The course of the disease was variable: eight stabilizations, two exacerbations, one cure and one improvement. DISCUSSION: This is the first series on childhood KA. Clinical characteristics were similar to those seen in adults. Impact was moderate and the disease course was variable. Systematic medical check-up for cystic fibrosis does not appear warranted in children since to date, cystic fibrosis has not been diagnosed in any patients presenting AK alone. CONCLUSION: AK is rare in children and should not cause erroneous concern, and improvement can occur.