Reprod Dom Anim. 2018;1–6. wileyonlinelibrary.com/journal/rda | 1 © 2018 Blackwell Verlag GmbH 1 | INTRODUCTION Disorders of sex development (DSDs) are responsible for sterility or infertility among domestic animals (Szczerbal & Switonski, 2016). These disorders can be caused by gene mutations or chromosome anomalies, as well as by other factors, such as placental anastomosis of heterosexual fetuses. The nomenclature of DSDs, initially devel‐ oped for humans (Hughes, Houk, Ahmed, & Lee, 2006) and adopted for dogs and cats (Poth, Breuer, Walter, Hecht, & Hermanns, 2010), is based on sex chromosome status related to gonadal and pheno‐ typic sex. Analysis of these chromosomes should therefore be the first step in diagnosis. A normal male sex chromosome complement (38,XY) has very often been observed in DSD cats (Nowacka‐Woszuk et al., 2014; Pienkowska‐Schelling, Becker, Pineroli, & Schelling, 2015; Reynolds et al., 2014; Schlafer et al., 2011). On the contrary, testicular XX Received: 22 March 2018 | Revised: 18 May 2018 | Accepted: 3 June 2018 DOI: 10.1111/rda.13263 ORIGINAL ARTICLE Disorders of sex development in cats with different complements of sex chromosomes Izabela Szczerbal 1 | Paulina Krzeminska 1 | Stanislaw Dzimira 2 | Tuire Maria Tamminen 3 | Seppo Saari 4 | Wojciech Nizanski 5 | Maciej Gogulski 6 | Joanna Nowacka‐ Woszuk 1 | Marek Switonski 1 1 Department of Genetics and Animal Breeding, Poznan University of Life Sciences, Poznan, Poland 2 Department of Pathology, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland 3 Department of Production Animal Medicine, University of Helsinki, Helsinki, Finland 4 Veterinary Histopathology Service Patovet Ay Kivihaantie 7, Helsinki, Finland 5 Department of Reproduction and Clinic of Farm Animals, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland 6 University Centre for Veterinary Medicine, Poznan University of Life Sciences, Poznan, Poland Correspondence Marek Switonski, Department of Genetics and Animal Breeding, Poznan University of Life Sciences, Poznan, Poland. Email: switonsk@up.poznan.pl Funding information Statutory fund of the Department of Genetics and Animal Breeding, Poznan University of Life Sciences, Poland, Grant/ Award Number: 508.534.00.0 Abstract The genetic background of disorders of sex development (DSDs) in cats is poorly understood, due to a relatively low number of such studies in this species. Here we present three new DSD cases with different complements of sex chromosomes. The first, an Oriental Shorthair cat with a rudimentary penis, abdominal atrophic testicles and lack of uterus appeared to be a freemartin, since leucocyte chimerism XX/XY and a lack of Y‐linked genes (SRY and ZFY ) were observed in DNA isolated from hair follicles. XXY trisomy was identified in the second case, a tortoiseshell Devon Rex male cat with atrophic scrotal testicles and a normal penis. Finally, a European Shorthair cat with atrophic testicles in a bifid scrotum, rudimentary penis and a lack of uterus had XY complement, including Y chromosome of normal size and morphol‐ ogy. Also presence of eight Y‐linked genes, detected by PCR, was confirmed. Due to the low testosterone level in this last patient, we searched for a causative mutation in two candidate genes (HSD3B2 and HSD17B3) involved in the metabolism of this steroid hormone. Altogether, five polymorphic sites in HSD3B2 and two in HSD17B3 were found, but none of them showed associations with DSD phenotype. We thus excluded a possibility that the causative mutation is present in these genes. In con‐ clusion, we confirmed that analysis of the sex chromosome complement is a crucial step in diagnosis of DSDs. However, extensive molecular studies of the genes in‐ volved in sex development are needed to elucidate the causes of DSDs in cats with normal complements of sex chromosomes. KEYWORDS aneuploidy, intersexuality, leucocyte chimerism, XXY trisomy