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BioMed Research International
Volume 2014, Article ID 195793, 8 pages
Research Article

Molecular Testing for Fragile X: Analysis of 5062 Tests from 1105 Fragile X Families—Performed in 12 Clinical Laboratories in Spain

1Laboratorio de Genética Molecular, Servicio de Genética, Hospital Universitario Cruces, BioCruces Health Research Institute, GCV-CIBER de Enfermedades Raras (CIBERER-ISCIII), Barakaldo, 48903 Bizkaia, Spain
2Unidad de Genética Molecular, Centro de Bioquímica y Genética Clínica, Hospital Clínico Universitario Virgen de la Arrixaca, El Palmar, 30120 Murcia, Spain
3Unidad de Genética, Hospital Universitario La Fe, 46009 Valencia, Spain
4Laboratorio de Genética, UDIAT-Centre Diagnòstic, Corporació Sanitària Parc Taulí, Institut Universitari UAB, Sabadell, 08208 Barcelona, Spain
5Unidad de Gestión Clínica de Salud Mental, Hospital Regional Universitario de Málaga, Instituto de Investigación Biomédica de Málaga (IBIMA), 29010 Málaga, Spain
6Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid, CSIC, 47003 Valladolid, Spain
7Consulta de Genética Clínica, Servicio de Pediatría, Hospital Clínico Universitario Lozano Blesa, Facultad de Medicina, Universidad de Zaragoza, GCV-CIBER de Enfermedades Raras (CIBERER-ISCIII), 50009 Zaragoza, Spain
8Servicio de Genética, Hospital Ramón y Cajal, 28034 Madrid, Spain
9Servicio de Biología Molecular, Hospital Virgen Macarena y Universidad de Sevilla, 41009 Sevilla, Spain
10Servicio de Genética, Hospital Universitari Son Espases, GCV-CIBER de Enfermedades Raras (CIBERER-ISCIII), Palma de Mallorca, 07010 Illes Balears, Spain
11Unidad de Genética Médica, Hospital Universitario Miguel Servet, 50009 Zaragoza, Spain
12Servicio de Genetica, IIS-Hospital Universitario Fundación Jiménez Díaz (IIS-FJD, UAM), CIBER de Enfermedades Raras (CIBERER-ISCIII), 28040 Madrid, Spain
13Servicio de Genética, Complejo Hospitalario de Navarra, 31008 Pamplona, Spain
14Servicio de Bioquímica y Genética Molecular, Hospital Clinic, IDIBAPS, CIBER de Enfermedades Raras (CIBERER-ISCIII), 08036 Barcelona, Spain

Received 23 February 2014; Accepted 27 April 2014; Published 28 May 2014

Academic Editor: Emin Karaca

Copyright © 2014 María-Isabel Tejada et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Fragile X syndrome is the most common inherited form of intellectual disability. Here we report on a study based on a collaborative registry, involving 12 Spanish centres, of molecular diagnostic tests in 1105 fragile X families comprising 5062 individuals, of whom, 1655 carried a full mutation or were mosaic, three cases had deletions, 1840 had a premutation, and 102 had intermediate alleles. Two patients with the full mutation also had Klinefelter syndrome. We have used this registry to assess the risk of expansion from parents to children. From mothers with premutation, the overall rate of allele expansion to full mutation is 52.5%, and we found that this rate is higher for male than female offspring (63.6% versus 45.6%; ). Furthermore, in mothers with intermediate alleles (45–54 repeats), there were 10 cases of expansion to a premutation allele, and for the smallest premutation alleles (55–59 repeats), there was a 6.4% risk of expansion to a full mutation, with 56 repeats being the smallest allele that expanded to a full mutation allele in a single meiosis. Hence, in our series the risk for alleles of 59 repeats is somewhat higher than in other published series. These findings are important for genetic counselling.