Molecular characterization of Spanish patients with MECP2 duplication syndrome.

MECP2 duplication syndrome (MDS) is an X-linked neurodevelopmental disorder characterized by a severe to profound intellectual disability, early onset hypotonia and diverse psycho-motor and behavioural features. To date, fewer than 200 cases have been published. We report the clinical and molecular characterization of a Spanish MDS cohort that included 19 boys and 2 girls. Clinical suspicions were confirmed by array comparative genomic hybridization and multiplex ligation-dependent probe amplification (MLPA). Using, a custom in-house MLPA assay, we performed a thorough study of the minimal duplicated region, from which we concluded a complete duplication of both MECP2 and IRAK1 was necessary for a correct MDS diagnosis, as patients with partial MECP2 duplications lacked some typical clinical traits present in other MDS patients. In addition, the duplication location may be related to phenotypic severity. This observation may provide a new approach for genotype-phenotype correlations, and thus more personalized genetic counselling.

A 11.7-Mb Paracentric Inversion in Chromosome 1q Detected in Prenatal Diagnosis Associated with Familial Intellectual Disability.

Most apparent balanced chromosomal inversions are usually clinically asymptomatic; however, infertility, miscarriages, and mental retardation have been reported in inversion carriers. We present a small family with a paracentric inversion 1q42.13q43 detected in routine prenatal diagnosis. Molecular cytogenetic methods defined the size of the inversion as 11.7 Mb and excluded other unbalanced chromosomal alterations in the patients. Our findings suggest that intellectual disability is caused by dysfunction, disruption, or position effects of genes located at or near the breakpoints involved in this inversion.

Mosaicos cromosómicos en vellosidad corial / Chromosomal mosaicism in chorionic villi

Introducción. El estudio de vellosidades coriales comprende realizar 2 cultivos celulares que pueden no tener resultados coincidentes. Estas discrepancias pueden ser debidas a mosaicos citogenéticos de origen in vivo o in vitro. En este trabajo nos planteamos analizar los cariotipos en mosaicos, ligado con los rendimientos de los cultivos celulares y los resultados citogenéticos. Material y métodos. Se han analizado 2.360 muestras prenatales y 510 de vellosidades de abortos. Con las muestras prenatales se efectúan rutinariamente 2 cultivos celulares, cultivo corto y cultivo largo, y para los abortos además se han estudiado muestras de restos fetales. Resultados. El porcentaje de muestras con resultado citogenético para el grupo prenatal fue del 99,9% y para el grupo de abortos del 87,1%. El porcentaje de anomalías cromosómicas en el grupo prenatal fue del 10,6% siendo las aneuploidías comunes (trisomías 13, 18, y 21) las más frecuentes, y para el grupo de abortos fue del 55,1% siendo las aneuploidías no-comunes las más frecuentes. El porcentaje de cariotipos en mosaico para el grupo prenatal fue del 3,1% y para el grupo de abortos del 6,8%. El mosaico confinado a la placenta tipo ii fue el más frecuente. Conclusiones. Para el estudio de los mosaicos en vellosidades coriales la mejor estrategia es realizar los 2 cultivos paralelos en muestras prenatales y los 3 cultivos en muestras de abortos. Teniendo en cuenta el riesgo que asume la pareja ante una prueba invasiva, es nuestro deber dar el resultado citogenético más completo posible(AU)

Introduction. The study of chorionic villus samples comprises performing two cell cultures that may not have matching results. These discrepancies may be due to cytogenetic mosaics of in vivo or in vitro origin. This study included analysing the karyotypes in mosaics, associated with the cell culture and cytogenetic results. Material and methods. Prospective study based on the analysis of 2,360 chorionic villus samples and 510 spontaneous abortion samples. Two cultures were routinely performed on the prenatal samples (short and long), as well as on the abortion samples. Results. The success rate was 99.9% in the prenatal group, and 87.1% in the abortion group. The percentage of chromosomal anomalies in the prenatal group was 10.6%, with the common aneuploidies (trisomy 13, 18, and 21) being the most frequent. In the abortions group there 55.1% anomalies, with uncommon aneuploidy the most frequent. The percentage of mosaicism in the prenatal group was 3.1%, and it was 6.8% in the abortion group. The confined placental mosaicism type ii was the most frequent. Conclusions. For the study of the mosaicism in chorionic villi samples the best strategy is to perform 2 prenatal samples cultures in parallel, and 3 abortion samples cultures. Given the risk to the mother and child using this invasive test, it is our duty to give the most comprehensive cytogenetic results achievable(AU)

Trisomy 18p caused by a supernumerary marker with a chromosome 13/21 centromere: a possible recurrent chromosome aberration.

We present a clinical and molecular cytogenetic characterization of two new patients with a complex supernumerary marker consisting of the entire short arm of chromosome 18 with a chromosome 13/21 centromere. One patient is a girl with a nonsyndromic intellectual disability and the second is a prenatally diagnosed fetus. To our knowledge, these are the fourth and fifth such cases to be described in the literature, suggesting the existence of a possible recurring constitutional structural chromosome abnormality.

Non-mosaic trisomy 20 of paternal origin in chorionic villus and amniotic fluid also detected in fetal blood and other tissues.

Trisomy 20 mosaicism is a common abnormality found in prenatal diagnosis. Its clinical significance remains unclear since approximately 90-93% of cases result in normal phenotype. Only 5 cases of non-mosaic trisomy 20 in amniotic fluid culture surviving beyond the first trimester have been reported. Moreover, trisomic cells are generally not detectable in blood and have only been reported in three cases. We present a case of non-mosaic trisomy 20 found in chorionic villi sample and amniotic fluid culture in a fetus with minor abnormalities not detected by ultrasound examination. Pathological examination of the fetus only revealed right pulmonary isomerism and camptodactily, and no major malformations were disclosed. Trisomic lineage was also detected in fetal blood, kidney, skin and brain tissue cultures. Molecular analysis revealed that the extra chromosome 20 was originated in paternal meiosis. To our knowledge, we report the first prenatal case of non-mosaic trisomy 20 of paternal origin that has been confirmed in several fetal tissues, including blood, in a fetus with minor malformations not detected prenatally.

Phylloid hypomelanosis and mosaic partial trisomy 13: two cases that provide further evidence of a distinct clinicogenetic entity.

BACKGROUND: Phylloid hypomelanosis is a rare neurocutaneous syndrome characterized by a pattern of hypopigmentation consisting of leaflike or oblong macules reminiscent of floral ornaments. Associated extracutaneous anomalies include cerebral, ocular, and skeletal defects. Recently it has been suggested that this phenotype originates from mosaic partial or complete trisomy 13. We report clinical and cytogenetic data for 2 cases. OBSERVATIONS: A bizarre pattern of multiple leaflike macules was noted in 2 girls with mental deficiency. In patient 1, additional anomalies included syndactyly, clinodactyly, trichomegaly of the eyelashes, low frontal hairline, and several pale pink telangiectatic macules. In patient 2, epileptic seizures, dental malposition, oligodontia, preauricular fistulas, scoliosis, tethered cord, and syringomyelia were noted. A diagnosis of phylloid hypomelanosis was made in both patients. In both patients, blood lymphocytes showed a normal karyotype 46,XX; however, fibroblasts derived from lesional skin demonstrated tetrasomy of chromosome 13q21-qter in patient 1 and trisomy of 13q22-qter in patient 2. CONCLUSIONS: These 2 cases lend further support to the concept that phylloid hypomelanosis is a distinct clinicogenetic entity that should no longer be confused with pigmentary mosaicism of the Ito type. From a comparison of our cytogenetic findings with those documented in previous articles, we infer that phylloid hypomelanosis is most likely related to the 13q region.