X monosomy in a Virilized Female Cat

An infertile Siamese female cat was subjected for clinical, histological, cytogenetic and molecular studies due to ambiguous external genitalia (vulva, vagina, rudimentary penis and scrotum‐like structure) and masculine behaviour. An elevated oestrogen activity and a detectable level of testosterone were found. The cat underwent laparotomy. The gonads and the uterus were removed and subjected for histological studies, which showed ovaries with corpora lutea and a some primordial follicles. Chromosome studies of lymphocyte and fibroblast cultures, with the use of Giemsa staining, G‐banding and whole X chromosome painting by fluorescence in situ hybridization, revealed pure X monosomy. Molecular analysis showed the absence of the SRY gene. Our study revealed for the first time that X monosomy in cats may be associated with virilization, in spite of the lack of the SRY gene.