[Cytogenetic and histologic examination of four tortoiseshell cats]

Tortoiseshell colored tomcats are very uncommon. In most cases their phenotype is caused by an aberration of sex chromosomes. In this study, we carried out cytogenetic investigations in four tortoiseshell tomacats. In two cases, an XXY syndrome could be proven. Another tortoiseshell tomcat had an XX/XY chromosomal constitution. One tomcat showed an exclusively male XY karyotype. In two cases the testes were histologically examined. In one XXY phenotypically male cat there was no spermatogenesis present. In the tomcat with XX/XY-chimerism spermatogenesis was seen in some testicular tubules.