Objective: To characterise the structurally abnormal Y chromosomes present in two infertile men by means of the molecular technique of fluorescence in-situ hybridisation (FISH).
Methods: Both men were phenotypically normal and had azoospermia. In Case 1 the karyotype with routine cytogenetics was 46,XX; in Case 2 it was complex, with 3 cell lines--45,X/46,X,i(Yp)/46,X,+?del(Y)(q11). We used probes from the Y chromosome and FISH to clarify these karyotypes.
Results: In Case 1 a translocation of Y chromosome to the X chromosome was identified with FISH--t(X;Y). In Case 2, an isochromosome of the short arm of the Y chromosome was confirmed in one cell line, and another cell line was shown to contain a small Y chromosome with heterochromatic deletion. These findings explained the underlying pathogenesis in both cases.
Conclusions: Molecular investigation with FISH should become part of the routine investigation of infertile men with an abnormal Y chromosome.