The case of an Sry-negative XX male Pug with an inguinal gonad

A case of intersexuality in a Pug that was bought as a male in a pet shop is described. The dog was presented at the Veterinary Teaching Hospital, University of Turin, for a reddish mass protruding from the prepuce. The mass had the aspect of an enlarged clitoris, with a caudoventral direction and a dorsal urethral ostium. A gonad was palpable in the left inguinal region. Laparotomy confirmed ultrasound detection of an abdominal uterine structure together with the right gonad. The histology of both gonads was similar, showing an exclusively masculine character, with seminiferous tubules lined only by Sertoli cells; the uterus showed a normal histological structure. Karyological analysis revealed a female karyotype (78,XX), and polymerase chain reaction showed the absence of Sry. The diagnosis was an XX male. The pathogenesis of the XX sex reversal syndrome in dogs is not completely understood, as Sry, the master gene regulating testis differentiation, is not present; to date, no genetic cause has been identified for this phenotypic condition in dogs. This case is unusual because the dog showed an inguinal testis, implying a partial activity of the mechanisms leading to abdominal testis translocation along a gubernaculum and transinguinal migration.