Trastornos neurológicos graves y malformaciones en una niña con monosomía del cromosoma 21 / Severe neurological disorders and malformations in a girl with mo- nosomía of the chromosome 21

Se presenta el caso de una niña de 7 años de edad, que fue remitida a la Consulta de Asesoramiento Genético, por presentar malformaciones congénitas severas y rasgos dismórficos, asociado a un retardo del neurodesarrollo. Al nacer se diagnosticó una comunicación interauricular, lo cual fue corregido mediante operación cardiaca. Se le realizó estudio por técnicas de citogenética convencional obteniéndose como resultado una monosomía del cromosoma 21. El estudio de citogenética molecular por técnica FISH detectó una inserción de la zona crítica del 21 en la región subtelomérica del 6p.

The case of a 7-year-old girl is showed. She was referral to the Genetic Advice Session, for presenting severe congenital malformations and dysmorphisms, associated with a neurological delay. A canal inter auricle was diagnosed at birth, which was corrected through heart surgery. The conventional cytogenetic analyzed showed a 21 chromosome monosomy. The study of molecular cytogenetic detected an insertion of the critical region of 21 in the subteloméric 6p region.

Antenatal cytogenetic testing in Havana, Cuba.

INTRODUCTION Antenatal cytogenetic testing was started in Havana in 1984, as a diagnostic option for fetal chromosome complement. The techniques applied are amniocyte culture, chorionic villus sampling, cordocentesis and fluorescence in situ hybridization in interphase cells. OBJECTIVE Describe the results of antenatal cytogenetic testing in the cytogenetic laboratory of the Cuba's National Medical Genetics Center in Havana, from 1984 through 2012. METHODS A retrospective descriptive study was carried out of the 22,928 pregnant women who had antenatal testing with conclusive results during the period 1984-2012. Information was obtained from laboratory databases for four antenatal diagnostic techniques. Variables studied were: antenatal diagnostic method, indications for genetic testing, type of chromosomal abnormality detected and couple's decision concerning pregnancy continuation if hereditary disease was diagnosed. Results were reported in absolute numbers and percentages. RESULTS Overall positivity was 2.8% (641 cases). Of the total, 20,565 samples were from amniocyte culture (558 positive cases, 2.7%); 1785 chorionic villus sampling (38 positive, 2.1%); 407 cord blood culture (28 positive, 6.9%); and 171 fluorescence in situ hybridization in interphase cells (17 positive, 9.9%). Advanced maternal age was the predominant indication for amniocyte culture and chorionic villus sampling. Positivity was higher for the two less frequently used methods, cordocentesis (6.9% positivity) and fluorescence in situ hybridization (9.9%). The predominant chromosomal abnormality was Down syndrome, with 45.4% of cases detected (291/641; 279 pure lines and 12 mosaic trisomies), followed by Edward syndrome with 12% (77/641, 71 pure lines and 6 mosaics) and Patau syndrome 4.7% (30/641, 27 pure lines and 3 mosaics). Sexual aneuploidy with pure lines affected 6.9% of cases (44/641) and with mosaicism 4.7% (30/641). Structural chromosomal abnormalities were detected in 22.5% of cases (144/641); of these, 70.8% (102/144) were balanced and 29.2% (42/144) unbalanced. In 78.6% of cases (504/641) with chromosomal abnormalities, whether mosaic or pure, the couple opted to terminate pregnancy. CONCLUSIONS Antenatal cytogenetic testing has helped reduce chromosomal abnormalities, mainly in Havana, and has provided reassurance of chromosomally normal children for couples at high genetic risk. The percentage of continuing pregnancies after a diagnosis of major chromosomal abnormality has been low, supporting evidence of broad population acceptance of abortion as an option when severe genetic abnormalities are present.

Mosaicismo de aneuploidías de los cromosomas sexuales en el diagnóstico prenatal / Mosaicism of aneuploidias of sexual chromosomes in prenatal diagnosis

El mosaicismo, de las aneuploidías sexuales es relativamente frecuente en el Diagnóstico Prenatal Citogenético, comparado con otros tipos de mosaicismos cromosómicos. En una serie de 16 950 amniocentesis se determinó la frecuencia de este tipo de mosaicismo en nuestro medio, su efecto en el fenotipo fetal y la influencia del porcentaje de la línea aberrada en la manifestación de malformaciones. Como resultado, se describen 18 casos de mosaicos sexuales para una frecuencia de 37,5(percent). El 50(percent) de los mismos correspondió a la aberración cromosómica 45,X/46,XX. Se detectó solo un 11,1(percent (2/18) de alteraciones fenotípicas, sin encontrar una influencia determinante del porcentaje de la línea aberrada. Se halló un alto índice de interrupciones de embarazos entre estos casos de mosaicismo de los cromosomas sexuales, lo cual no coincide con los reportes de la literatura…(AU)