A case of leucocyte chimerism (78,XX/78,XY) in a dog with a disorder of sexual development

A 1-year-old Shih Tzu dog was presented for examination because of abnormal external genitalia. A residual penis with a prepuce was located in a position typical of a male. The dog had no palpable testicles or scrotum. The ultrasound examination revealed the presence of the prostate, but the gonads remained undetectable. Cytogenetic analysis performed on chromosome preparations obtained from lymphocyte culture showed two cell lines - 78,XX and 78,XY. Molecular analysis of 14 polymorphic microsatellite markers allowed us to distinguish leucocyte chimerism from whole body chimerism. The presence of 3 or 4 alleles was confirmed in DNA isolated from blood, while in DNA isolated from hair follicles only 1 or 2 alleles were detected. The case was classified as leucocyte 78,XX/78,XY chimerism. Our study showed that XX/XY leucocyte chimerism might be associated with disorder of sexual development in dogs. Furthermore, it is emphasized that the use of cytogenetic study, in combination with analysis of polymorphic markers in DNA isolated from different somatic cells, facilitates distinguishing between leucocyte and whole body chimerism.