Characterisation, phenotypic manifestations and X-inactivation pattern in 14 patients with X-autosome translocations

Here we describe a group of 14 patients carrying different X-autosome trans locations and exhibiting phenotypes that demonstrate the range of alteratio ns induced by such aberrations. All male carriers of an X-autosome transloc ation in our investigation group were infertile, whereas fertility in the f emale carriers was dependent on the position of the break-point in the X ch romosome. Fertile women with translocation break-points outside of the crit ical region (Xq13-q26) in some cases passed on the translocation to their o ffspring. In balanced female carriers in our group, the normal X chromosome was usually inactivated, allowing full expression of genes on the transloc ated segments. In one case, disruption of the dystrophine gene in Xp21 led to the manifestation of Duchenne muscular dystrophy in a female carrier. In activation of the derivative X (X,) in a balanced female carrier led to a p artial monosomy of the autosome/disomy of the X chromosome and resulted in an aberrant phenotype. In unbalanced carriers, X, is generally late-replica ting:inactive, although failed spreading of inactivation to the autosomal s egment often results in a partial trisomy, as evidenced by the case of an u nbalanced translocation carrier in our group.