RESUMO
The human X chromosome carries regions prone to genomic instability: deletions in the Xp22.31 region, involving the steroid sulfatase gene (STS) cause X-linked ichthyosis; rearrangements in the Xp21.2 region are associated with Duchenne or Becker muscular dystrophies (DMD or BMD); and the Xq27.3 unstable region, containing the (CGG)n repeat expansion in the FMR1 gene is associated with fragile X syndrome. We report on a family with two affected boys, the elder diagnosed with fragile X syndrome, the younger with DMD, and both suffering from severe ichthyosis. The family was analyzed by polymerase chain reaction, multiplex ligation-dependent probe amplification and haplotype analysis. The mother proved to be an asymptomatic carrier of all three non-contiguous mutation events, involving the STS gene, the DMD gene and a FMR1 expansion. To the best of our knowledge, this is the first description of an asymptomatic carrier of three different X-linked disorders, involving severe genetic rearrangements on both long and short arms of the X chromosomes. The boy with fragile X syndrome has inherited a triple recombinant maternal X chromosome, this way inheriting the FMR1 expansion and ichthyosis, originating most probably from different maternal Xes and excluding the DMD gene deletion. The transmission of these extremely defective maternal chromosomes to the next generation involved several recombinations.
Assuntos
Síndrome do Cromossomo X Frágil/genética , Heterozigoto , Ictiose/genética , Padrões de Herança , Distrofia Muscular de Duchenne/genética , Adulto , Criança , Metilação de DNA , Feminino , Proteína do X Frágil da Deficiência Intelectual/genética , Haplótipos , Humanos , Masculino , Mutação , Nucleotidases , Proteínas/genética , Esteril-Sulfatase/genética , Expansão das Repetições de TrinucleotídeosAssuntos
Deficiência Intelectual/genética , Mutação , Bulgária , Feminino , Heterogeneidade Genética , Genótipo , Humanos , Masculino , FenótipoRESUMO
Mesomelic form of chondrodysplasia and congenital glaucoma associated with de novo translocation (13;18)(q14:q23): Mesomelic dysplasias are characterized by limb shortening most prominent of the middle segment of the extremities (forearm and lower leg). In addition to several syndromic forms a few patients with sporadic or familial forms and without precise nosological classification have been reported so far. In this report we present a young female with disproportionate mesomelic dwarfism, dysmorphic facial features, bilateral glaucoma, patent ductus arteriosus, low and hoarse voice, and generalized muscular hypotonia. At the age of 2.5 years mental development is normal. High resolution G-banded chromosome studies revealed a de novo reciprocal translocation with karyotype 46,XX t (13;18)(q14;q23). The concurrence of this de novo autosomal translocation with this distinct phenotype supports the hypothesis that disruption of (a) gene(s) at the translocation breakpoints causes this unusual, apparently new form of skeletal chondrodysplasia.