Abstract for presentation at 11th International Congress of Human Genetics

Small Supernumerary X Chromosome in a Boy with Mild Phenotype

  • Hironao Numabe, Department of Biomedical Ethics, Kyoto University Graduate School of Medicine, Japan
  • Hirofumi Ohashi, Division of Medical Genetics, Saitama Children’s Medical Center, Japan
  • Norimasa Mitsui, Department of Clinical Laboratory, Saitama Children’s Medical Center, Japan
  • Hisashi Kawashima, Department of Pediatrics, Tokyo Medical University, Japan
  • Shin Hayashi, Department of Molecular Cytogenetics, Medical Research Institute, Tokyo Medical and Dental University, Japan
  • Issei Imoto, Department of Molecular Cytogenetics, Medical Research Institute, Tokyo Medical and Dental University, Japan
  • Johji Inazawa, Department of Molecular Cytogenetics, Medical Research Institute, Tokyo Medical and Dental University, Japan
  • Shinji Kosugi, Department of Biomedical Ethics, Kyoto University Graduate School of Medicine, Japan

    • A 3-year-old boy with a 47,XY,+der(X)[22]/46,XY[8] karyotype. Fluorescence in situ hybridization (FISH) with a whole X chromosome painting probe confirmed that the small supernumerary marker chromosome was X-derived. Additional FISH with ten X-specific probes revealed that the derivative chromosome was ish der(X)(MAOB-, CDPX2-, SMCX+, DXS423E+, ZXDA+, DXZ1+, AR-, ED1-, XIST-, CHM-), and was probably a ring chromosome. Recent result of the MCG (Matrix-Comparative Genomic Hybridization) X-tiling array which covers whole X chromosome by 1003 BAC clones revealed that duplicated segment of X chromosome was between Xp11.22 and Xp11.1. Our case has few minor malformations such as arched eyebrows, hypertelorism, epicanthal folds, low-set ears, a short nose with depressed nasal tip, a long philtrum, a small mouth, clinodactyly of bilateral fifth fingers, soft tissue syndactyly of the left second and third toes, and mental retardation mainly caused by the speech delay. A partial functional disomy of X chromosome caused by the lack of XIST was thought to cause these symptoms.

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