Results
Pet health test
Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis

Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis

Keratoconjunctivitis sicca congenita and ichthyosiform dermatosis (QSCDI) is a condition identified in the Cavalier King Charles Spaniel breed. This condition is characterized by a combination of ocular dryness and tear film loss, along with a skin disorder manifested by scaly skin and a rough, curly coat.

Symptoms

The first clinical signs of this disorder usually manifest at an early age, with puppies reported to have difficulty opening their eyes as early as 10 to 11 days of age. Symptoms associated with congenital keratoconjunctivitis sicca include redness in one or both eyes and the presence of a dense, mucopurulent ocular discharge. In severe cases, these symptoms may progress to corneal ulceration followed by corneal vascularization. From the time of birth, these dogs exhibit an abnormal coat, characterized by a rough, alopeciated and curly coat. The skin, especially along the dorsal spine and flanks, is often dry and scaly. In adulthood, hyperpigmentation of the skin of the abdominal belly and hyperkeratinization of the plantar pads are observed. In addition, dental problems and alterations in nail growth with possible detachment have been reported.

Disease Management

There are no preventive measures for this condition, and management of the disease is a challenge, as it requires intensive care by the owner. The dermatological prognosis is unfavorable and complete cure is not achieved. In the treatment of keratoconjunctivitis, topical immunomodulatory drugs and lacrimal substitutes are commonly used. Some caregivers have observed that regular nail trimming appears to reduce nail detachment, as well as, the use of essential fatty acid supplements (flaxseed oil) are beneficial to skin health. In addition, it is advisable to maintain a regular dental care routine.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis is an autosomal recessive disorder associated with a mutation in the FAM83H gene. Keratoconjunctivitis sicca appears to be the consequence of a neurofunctional defect of the lacrimal glands, resulting in decreased aqueous tear production. Whereas, ichthyosiform dermatosis develops from an abnormal increase in cell turnover in the outermost layer of the epidermis. The clinical findings observed in affected dogs suggest that the FAM83H gene plays a key role in the development and regulation of the skin, as well as in the formation of tooth enamel. The variant identified in the FAM83H gene responsible for this condition involves the deletion of a single base in exon 5, causing truncation of the peptide from 1151 to 528 amino acids. Although this mutation is believed to have originated exclusively in the Cavalier King Charles Spaniel breed, a larger number of breeds need to be examined to confirm this fact.

Most affected breeds

King Charles Cavalier Spaniel

Bibliography

Barnett KC. Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis in the cavalier King Charles spaniel. J Small Anim Pract. 2006 Sep;47(9):524-8.

Forman OP, Penderis J, Hartley C, et al. Parallel mapping and simultaneous sequencing reveals deletions in BCAN and FAM83H associated with discrete inherited disorders in a domestic dog breed. PLoS Genet. 2012 Jan;8(1):e1002462.

Hartley C, Donaldson D, Smith KC, et al. Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis in 25 Cavalier King Charles spaniel dogs. Part I: clinical signs, histopathology, and inheritance. Vet Ophthalmol. 2012 Sep;15(5):315-26.