ESPE Abstracts (2015) 84 FC2.3

High Success of a Next Generation Sequencing Panel for the Molecular Diagnosis of Rare Skeletal Dysplasias

Jimena Barrezaa,b, Carlos I Rivera-Pedrozaa, Lucia Sentchordi-Montanéa,c, Elena Vallespina,b, Victoria E F Montañoa, Elena Mansillaa,b, Alberta Belinchóna,b, Sara Benito-Sanza,b, Angela del Pozoa,b, Kristina Ibañeza, Isabel González-Casadod, Encarna Guillén-Navarroe, Pablo Prietof, Jaime Sánchez del Pozog, Jaime Cruz-Rojog, Enrique Galanh, Pablo Lapunzinaa,b, Sixto García-Miñaura,b, Fernando Santos-Simarroa,b & Karen E Heatha,b

aInstitute of Medical and Molecular Genetics (INGEMM) and UMDE, IdiPAZ, Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid, Spain; bCIBERER, ISCIII, Madrid, Spain; cDepartment of Pediatrics, Hospital Universitario Infanta Leonor, Madrid, Spain; dDepartment of Pediatric Endocrinology and UMDE, Hospital Universitario La Paz, Madrid, Spain; eDepartment of Genetics, Hospital Virgen de la Arrixaca, Murcia, Spain; fDepartment of Pediatric Endocrinology, Hospital Universitario de Salamanca, Salamanca, Spain; gDepartment of Pediatric Endocrinology and Dysmorphology, Hospital Universitario 12 de Octubre, Madrid, Spain; hDepartment of Clinical Genetics, Hospital Materno Infantil de Badajoz, Badajoz, Spain; iDepartment of Pediatric Endocrinology, Hospital Terrassa, Terrassa, Spain

Background: A total of 456 skeletal dysplasias have been classified by molecular, biochemical and/or radiological criteria, into 40 groups. Despite this, the precise, final diagnosis is often difficult due to the high phenotypic and genotypic variability.

Objective: To improve the molecular and clinical diagnosis of skeletal dysplasias using a custom-designed next-generation sequencing (NGS) panel.

Method: A total of 56 skeletal dysplasia probands of unknown molecular etiology were clinically and radiologically evaluated. DNA from the probands and in some cases affected family members, was analysed using the SKELETALSEQ.V3 panel (n=315 genes) and sequenced on a MiSeq. All variants were confirmed by Sanger sequencing or arrayCGH. Functional analysis was undertaken where possible.

Results: In 24/56 (43%) probands the causative mutation(s) was identified; 12/25 (48%) probands classified with a severe and 12/31 (39%) with a mild skeletal dysplasia. A total of 23 missense, stop or small deletions and one gene deletion were detected. Two heterozygous stop mutations were identified in aggrecan (ACAN1) in two families with disproportionate short stature, one with advanced bone age whilst the other not. Compound heterozygous functionally confirmed pathogenic POP1 mutations were detected in the second case of spondylometaphyseal dysplasia with extreme short stature (−5.57 SDS) reported so far. Two novel homozygous POCA1 mutations were identified in two families with remarkably similar clinical features of primordial dwarfism (SOFT syndrome).

Conclusion: i) The SKELETALSEQ NGS panel is a powerful tool in determining the causative mutation in 43% of patients with skeletal dysplasias and extreme short stature. ii) Causative mutations were identified in genes in which only one or few mutations have been previously described. iii) The advancement in the genetic diagnosis of these disorders will not only improve the management, monitoring and treatment of these patients but also permit prenatal and preimplantational genetic studies for the affected families.

Funding: This work was supported in part by the following grants: MINECO (SAF2012-30871) and Comunidad de Madrid ENDOSCREEN (S2010/BMD-2396).

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