Genetic basis of Curly Coat Dry Eye Syndrome - in the Cavalier King Charles Spaniel it is an autosomal recessive genetic disorder caused by a mutation in the FAM83H gene. Both parents must carry the mutated gene for offspring to be affected. DNA testing can identify clear, carrier, and affected animals; though rare among CKCS, a significant percentage are carriers, making informed breeding critical to limiting its spread.
Pathophysiology - The FAM83H gene mutation disrupts normal keratin disassembly and tear production, leading to: Severely reduced aqueous tears: causing chronic dry eye, tacky/mucoid ocular discharge, corneal ulceration, and pain. Ichthyosiform dermatosis: abnormal skin keratinization resulting in persistent scaling, frizzy/rough/alopecic coat, and hyperkeratotic, hyperpigmented skin and footpads. Nail abnormalities: malformed nails are often present. Symptoms are usually evident between 2-10 weeks of age, with escalating signs as the dog matures.
Complications - Affected animals suffer significant morbidity: Ocular: recurrent infections, painful ulcerations, progressive vision loss. Dermatological: intense pruritus, scaling, cracking of paw pads, painful lameness. Quality of life: most dogs experience severe, progressive discomfort; euthanasia is common for welfare reasons in severe cases. Dental: higher incidence of dental disease has been noted in adulthood.
Why This Matters to Breeders and Vets - Breeders must use DNA testing to avoid breeding carriers and especially affected animals, since the syndrome is debilitating and easily preventable. Veterinarians need to recognize early signs, provide supportive treatment for symptoms, and educate owners and breeders about responsible genetic management. Breed-specific risk: The syndrome appears unique to CKCS and is rarely seen outside this breed, underscoring the importance of targeted genetic counseling.
Summary - Curly Coat Dry Eye Syndrome in Cavalier King Charles Spaniels is a serious, congenital, autosomal recessive disorder due to a mutation in the FAM83H gene. It results in life-long, severe eye and skin disease starting in puppyhood, with profound welfare implications. DNA testing offers an effective means to eliminate the disorder from breeding populations, making diagnostic awareness and genetic management essential for breeders and veterinarians.