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A case of mosaic Down's syndrome with two Robertsonian translocations
C H Leal-Garza1, E I Cortés-Gutiérrez, R Ortiz-Jalomo
1Centro de Investigación Biomédica del Noreste, Instituto Mexicano del Seguro Social, Monterrey N.L. México.
Abstract:
A baby with stigmata of Down's syndrome was found to be a mosaic with two different cell lines: 45,XX,der(14q;21q)/46,XX,der(21q;21q)+21. The chromosome rearrangements appeared to have risen de novo. Four mechanisms are discussed for the origin of the mosaicism: dissociation of a translocation (14q;21q) chromosome already present in the 45,XX, der(14q;21q) zygote; two translocation events occurring sequentially at the first and second zygote (46,XX) divisions; a chromatid translocation in a 47,XX,+21 zygote; and an independent origin of the two cell lines.