A rare finding of double Barr bodies and X-monosomy/X-trisomy mosaicism in a dog with presumed idiopathic epilepsy.

A 4-year-old spayed female Border Collie dog presented to the Neurology and Neurosurgery service for an approximately five-month history of seizures. A complete neurodiagnostic workup was performed and did not reveal any significant abnormalities. The patient's seizures were well controlled with a combination of anticonvulsants. During a manual blood smear review at a follow-up appointment, double Barr bodies were identified in segmented neutrophils. Karyotyping revealed that the patient is mosaic for X-monosomy and X-trisomy, a finding that has never been reported in a dog and is rarely reported in people. This case demonstrates how the identification of abnormal neutrophil nuclear appendages may correlate with chromosomal abnormalities in dogs.