Feline primary erythrocytosis (PE) is a rare myeloproliferative disorder causing excessive increase in packed cell volume (PCV). Veterinary literature is sparse with isolated reports and minimal information regarding prognosis. We evaluated a retrospective multicentre case series of feline PE, with the aim of increasing understanding of disease progression to guide management and prognostication. Theories of possible underlying genetic causes were evaluated by comparing the natural history of feline PE to human polycythaemia vera (PV).

Cases required documentation of increased PCV (>48%), sufficient investigation to exclude relative and secondary erythrocytosis, and follow-up data for at least twelve months or until death.

Eighteen cats from five UK veterinary hospitals were included. No significant trends in signalment were noted. Seizures and mentation changes were the most common presenting signs (both n=10). Median PCV and total protein were 70% and 76 g/l, respectively, with no other consistent blood cell changes. Sixteen cats survived to discharge. Phlebotomy was performed initially in 15/16 cats and after discharge in 10/16. Six cases eventually required no further phlebotomies. Hydroxyurea was the most common adjunctive therapy (n=10). Fourteen patients were alive at the time of writing (survival time >12 months).

This case series demonstrates that management of feline PE is generally well-tolerated with evidence of prolonged survival times. Disease characteristics are similar to a subset of human PV caused by mutations in exon 12 of the Janus kinase 2 gene, representing a possible future therapeutic target.

Disclosures

No disclosures to report.