Part of the official UK Kennel Club testing scheme in Cavalier King Charles Spaniel
Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis (CKCSID) is more commonly referred to as ‘‘curly coat dry eye syndrome’’. The disease is congenital; puppies are born with an abnormally rough/curly coat and are usually smaller than littermates. Affected dogs have reduced production of aqueous tears (keratoconjuncitivits sicca commonly called “dry eye”), a tacky mucoid discharge around their eyes and ulceration of the cornea in severe cases. They also have persistent scaling of the skin (ichthyosiform dermatosis) causing them to scratch.
The disease is progressive and beings to affect footpads and teeth. It is difficult to manage, and many owners choose to euthanise affected dog’s due poor quality of life.
The single nucleotide deletion in the gene called FAM83H that causes Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis (CKCSID) in many breeds is recessive. This means that dogs that carry two copies of the mutation (homozygotes) will almost certainly develop CKCSID during their lives. Dogs that carry a single copy of the mutation (also known as carriers or heterozygotes) will not develop CKCSID as a result of the FAM83H mutation, but they will pass the mutation onto about half of any offspring they have. Breeding dogs that will not develop CKCSID should be the breeder’s priority, with a reduction in mutation frequency within the whole breed being the secondary, longer-term target.
Carriers can be bred from safely, provided they are mated to a dog that has also been tested and is clear of the FAM83H mutation (i.e. carry no copies of the mutation). If a carrier is mated to a clear dog approximately half of the resulting puppies will also be carriers, so should be tested themselves prior to breeding. Breeding carriers to tested, clear dogs is safe, in terms of avoiding dogs affected with CKCSID, and will help to maintain the genetic diversity of a breed. It is therefore encouraged, particularly in the first few generations following the availability of a new genetic test, so that other desirable characteristics and traits can be preserved before the frequency of the disease mutation within the breed is gradually reduced.