RESUMEN
We report on a prenatally diagnosed unusual case of inverted terminal duplication of the short arm of chromosome 2, leading to interstitial telomeric sequences (ITSs) and partial trisomy 2p. To our knowledge, there are only 4 further cases of pure partial trisomy 2p reported prenatally. Here, the mother was referred at 22 weeks of gestation for isolated fetal congenital heart malformation at ultrasound. The karyotype of amniotic fluid cells displayed a large duplication of the short arm of chromosome 2 that was further investigated by array-CGH, which detected a 1-copy gain of 43.75 Mb in chromosome 2 at 2p21p25.3. FISH confirmed the presence of an inverted duplication in the short arm of chromosome 2 involving the region 2p21pter and revealed the presence of ITSs at the breakpoint in chromosome 2p21. This report contributes to the prenatal description of the syndrome. We also discuss the possible mechanisms leading to this duplication and the formation of ITSs which are rarely described in constitutional rearrangements.
Asunto(s)
Cromosomas Humanos Par 2/genética , Enfermedades Fetales/genética , Diagnóstico Prenatal , Telómero/genética , Trisomía/genética , Bandeo Cromosómico , Hibridación Genómica Comparativa , Femenino , Enfermedades Fetales/diagnóstico , Humanos , Hibridación Fluorescente in Situ , Embarazo , Trisomía/diagnósticoRESUMEN
FG syndrome, Lujan syndrome, and Ohdo syndrome, the Maat-Kievit-Brunner type, have been described as distinct syndromes with overlapping non-specific features and different missense mutations of the MED12 gene have been reported in all of them. We report a family including 10 males and 1 female affected with profound non-specific intellectual disability (ID) which was linked to a 30-cM region extending from Xp11.21 (ALAS2) to Xq22.3 (COL4A5). Parallel sequencing of all X-chromosome exons identified a frameshift mutation (c.5898dupC) of MED12. Mutated mRNA was not affected by non-sense mediated RNA decay and induced an additional abnormal isoform due to activation of cryptic splice-sites in exon 41. Dysmorphic features common to most affected males were long narrow face, high forehead, flat malar area, high nasal bridge, and short philtrum. Language was absent or very limited. Most patients had a friendly personality. Cognitive impairment, varying from borderline to profound ID was similarly observed in seven heterozygous females. There was no correlation between cognitive function and X-chromosome inactivation profiles in blood cells. The severe degree of ID in male patients, as well as variable cognitive impairment in heterozygous females suggests that the duplication observed in the present family may have a more severe effect on MED12 function than missense mutations. In a cognitively impaired male from this family, who also presented with tall stature and dysmorphism and did not have the MED12 mutation, a 600-kb duplication at 17p13.3 including the YWHAE gene, was found in a mosaic state.
Asunto(s)
Anomalías Múltiples/genética , Agenesia del Cuerpo Calloso/genética , Ano Imperforado/genética , Blefarofimosis/genética , Blefaroptosis/genética , Estreñimiento/genética , Enfermedades Genéticas Ligadas al Cromosoma X , Cardiopatías Congénitas/genética , Discapacidad Intelectual/genética , Complejo Mediador/genética , Discapacidad Intelectual Ligada al Cromosoma X/genética , Hipotonía Muscular/congénito , Proteínas 14-3-3/genética , Anomalías Múltiples/fisiopatología , Adulto , Anciano , Agenesia del Cuerpo Calloso/fisiopatología , Ano Imperforado/fisiopatología , Blefarofimosis/fisiopatología , Blefaroptosis/fisiopatología , Cromosomas Humanos X/genética , Estreñimiento/fisiopatología , Exones , Femenino , Mutación del Sistema de Lectura , Cardiopatías Congénitas/fisiopatología , Humanos , Discapacidad Intelectual/fisiopatología , Masculino , Discapacidad Intelectual Ligada al Cromosoma X/fisiopatología , Persona de Mediana Edad , Hipotonía Muscular/genética , Hipotonía Muscular/fisiopatología , Mutación , Inactivación del Cromosoma X/genéticaRESUMEN
This is the first report of a fetus affected with campomelic acampomelic dysplasia presenting with increased nuchal translucency. Ultrasonography at 13 weeks of amenorrhea showed a nuchal translucency 5.6 mm thick. The karyotype performed on amniotic fluid cells was normal (46,XY). Ultrasonography at 22 weeks revealed a normal femoral length and female genitalia. A second amniocentesis was performed to confirm the karyotype and for dosage of steroid hormones. Testosterone dosage was low, corresponding to a female fetus. Ultrasonography at 32 weeks showed growth retardation of the long bones (< 3rd centile) that were not curved. A severe malformation syndrome was suspected and the pregnancy was terminated at 33 weeks. The fetus displayed macrocephaly, facial dysmorphism and female external genitalia. X ray showed straight and thickened long bones, hypoplastic scapulae and moderate platyspondyly. In view of the association of sex reversal, hypoplasia of the scapulae, and the presence of straight long bones, campomelic acampomelic dysplasia was suspected and confirmed by the finding of a SOX9 mutation. This case shows the importance of a careful echographic survey in a fetus with a nuchal translucency > 4 mm, especially if there is discordance between phenotypic and genotypic sex, since growth retardation may occur later during the pregnancy.
