Pigmentary keratitis and mixed chromatophoroma in a betta fish ( Betta splendens )

Abstract Betta fish ( Betta splendens ) are common pets selectively bred for many different anatomic morphologies and colourations. Fish fanciers on hobbyist forums have linked certain phenotypic traits to the development of eye disease and neoplasia in this species. An 8‐month‐old male giant koi dragonscale plakat betta fish presented for ocular abnormalities and a mass on the tail. Clinical signs continued to progress, and the patient was euthanized due to declining quality of life 10 weeks after initial presentation. Pigmentary keratitis, anterior uveitis, and a mixed chromatophoroma were identified histologically. A review of the anecdotal and available scientific literature revealed that both the neoplastic disease and ocular disease may have had a genetic cause in this particular colour morph. Genetic disease should remain a differential for the cause of ocular and skin pathology in bettas. Combining genetic lines of fish may result in the development of multiple health problems, and ethical fish breeders should select away from characteristics that decrease lifespan and affect quality of life.