Male pseudohermaphroditism in a Labrador Retriever, and a review of mammalian sexual differentiation

Abstract

CASE HISTORY: An 8-month-old Labrador Retriever was referred with a history of ambiguous external genitalia.

CLINICAL FINDINGS AND TREATMENT: Clitoromegaly within apparent vulval folds, and an adjacent subcutaneous mass were noticed on external examination. An intra-abdominal testicle, with epididymis and suspected vas deferens ducts, was found during exploratory celiotomy. Incision over the subcutaneous mass revealed the accompanying testicle. Clitoridectomy was performed and an os clitoris removed. Normal juvenile testes were diagnosed on histology of the gonads. Chromosomal studies revealed a normal 78, XY male chromosomal constitution. Due to the combination of a male karyotype (78, XY), the presence of testicular tissue in the gonads, and the appearance of the external genitalia, a diagnosis of male pseudohermaphroditism (MPH) was made.

CLINICAL RELEVANCE: This case presents the first report of MPH in a Labrador Retriever, and highlights the diagnostic steps recommended when confronted with a dog with ambiguous external genitalia.

KEY WORDS:

• Pseudohermaphrodite
• intersex
• os clitoris
• testicular feminisation
• canine
• Labrador Retriever

Acknowledgements

The author would like to acknowledge Pfizer New Zealand for their continued support of the Pfizer Internship Programme at the Veterinary Specialist Group. We also wish to thank Dr Keith McSporran for contributing the histopathological findings, Dr Bill Reid for referral of the patient, and Dr Vicki Meyers-Wallen for her assistance with this case. Karyotyping and Sry gene sequencing were performed by Dr BP Chowdhary, Molecular Cy-togenetics Lab, Texas A&M University, USA.