Geneviève Pierquin

Germline PTPN11 missense mutation in a case of Noonan syndrome associated with mediastinal and retroperitoneal neuroblastic tumors

Noonan syndrome (NS) is an autosomal dominant disorder characterized by short stature, typical craniofacial dysmorphism, skeletal anomalies, congenital heart defects, and predisposition to malignant tumors. In approximately 50% of cases, the disease is caused by missense mutations in the PTPN11 gene. To date, solid tumors, and particularly brain tumors and rhabdomyosarcomas, have been documented in patients with NS; however, few cases of neuroblastoma associated with NS have been reported. Here we report an unusual case of neuroblastoma with mediastinal, retroperitoneal, and medullar locations associated in a NS patient carrying a PTPN11 germline missense mutation (p.G60A). This missense mutation occurs within the N-SH2 domain of the PTPN11 gene and has been reported to be associated with acute leukemia in NS patients. The association of this p.G60A PTPN11 mutation with neuroblastoma provides new evidence that gain of function PTPN11 mutations may play an important role in the pathogenesis of solid tumors associated with Noonan syndrome.

Spinocerebellar Ataxia Type 2 (SCA2): Clinical Features and Genetic Analysis

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disease that results from the expansion of an unstable trinucleotide CAG repeat encoding for a polyglutamine tract. In normal individuals, alleles contain between 14 and 31 CAG repeats, whereas the pathological alleles have more than 35 CAG repeats. The clinical phenotype of SCA2 includes a progressive cerebellar ataxia with additional features such as ophthalmoplegia, extra-pyramidal or pyramidal signs and peripheral neuropathy. We report a SCA2 large African family with several affected individuals. A major pathological allele carrying 43 CAG repeats was identified in the proband. To our knowledge, this is a first report of a SCA disorder described in Central African patients, thus indicating the need to consider this diagnosis in young African ataxic patients.

A new 48, XXYY/47, XYY syndrome associated with multiple skeletal abnormalities, congenital heart disease and mental retardation.

While the XYY and XXYY syndromes have been several time described in patients, the combination of both syndromes in an individual is a rare event and may result in a severe phenotype. In the present observation, a boy with congenital scoliosis due to segmented thoracic hemivertebra associated with radioulnar synostosis and congenital heart disease is described. Chromosome G-banding and FISH analysis demonstrated a de novo mosaic karyotype 48, XXYY/47, XYY in this patient. To the best of our knowledge, this is the first report of a combination of XYY and XXYY syndromes.

Diagnostic strategy in segmentation defect of the vertebrae: a retrospective study of 73 patients

Background Segmentation defects of the vertebrae (SDV) are non-specific features found in various syndromes. The molecular bases of SDV are not fully elucidated due to the wide range of phenotypes and classification issues. The genes involved are in the Notch signalling pathway, which is a key system in somitogenesis. Here we report on mutations identified in a diagnosis cohort of SDV. We focused on spondylocostal dysostosis (SCD) and the phenotype of these patients in order to establish a diagnostic strategy when confronted with SDV. Patients and methods We used DNA samples from a cohort of 73 patients and performed targeted sequencing of the five known SCD-causing genes (DLL3, MESP2, LFNG, HES7 and TBX6) in the first 48 patients and whole-exome sequencing (WES) in 28 relevant patients. Results Ten diagnoses, including four biallelic variants in TBX6, two biallelic variants in LFNG and DLL3, and one in MESP2 and HES7, were made with the gene panel, and two diagnoses, including biallelic variants in FLNB and one variant in MEOX1, were made by WES. The diagnostic yield of the gene panel was 10/73 (13.7%) in the global cohort but 8/10 (80%) in the subgroup meeting the SCD criteria; the diagnostic yield of WES was 2/28 (8%). Conclusion After negative array CGH, targeted sequencing of the five known SCD genes should only be performed in patients who meet the diagnostic criteria of SCD. The low proportion of candidate genes identified by WES in our cohort suggests the need to consider more complex genetic architectures in cases of SDV.

Rapid prenatal diagnosis of fetal Zellweger syndrome by biochemical tests, complementation studies, and molecular analyses

Molecular Genetics, Department of Human Genetics, CHU Sart-Tilman, University of Liège, Belgium Clinical Genetics, Department of Human Genetics, CHU Sart-Tilman, University of Liège, Belgium Department of Pathology, CHU Sart-Tilman, University of Liège, Belgium Department of Gynecology-Obstetrics, CHR Citadelle, Liège, Belgium Department of Medical Imaging, CHR Citadelle, Liège, Belgium Laboratory Genetic Metabolic Diseases, Academic Medical Center, Amsterdam, The Netherlands Metabolic Unit, Department of Human Genetics, CHU Sart-Tilman, University of Liège, Belgium *Correspondence to: François-Guillaume Debray. E-mail: fg.debray@chu.ulg.ac.be