Curly Coat Dry Eye Syndrome
Curly coat syndrome is a severe congenital condition of the skin, coat, claws, and eyes in some cavalier King Charles spaniel puppies. It is also known as rough coat syndrome and its scientific name is ichthyosis keratoconjunctivitis sicca and also as congenital keratoconjunctivitis sicca and ichthyosiform dermatosis (CKCSID).
In a May 2012 study of the DNA of 2,803 cavaliers, less than 0.15% were affected with the mutated gene causing curly coat syndrome, but over 8% of cavaliers were found to carry the defective gene. In a June 2012 report of DNA testing of 280 cavaliers, the UK's Animal Health Trust researchers estimate that 10.8% of CKCSs are carriers of curly-coat, and 0.4% are affected. It includes a very severe form of dry eye syndrome, but it is to be distinguished from the much more common form of dry eye in the CKSC breed.
No cases of curly coat syndrome with severe dry eye have been reported in any other breed. Studies have been conducted in the United States, United Kingdom, Australia, Sweden, the Czech Republic, and Iceland. During a two year period recently in Iceland, more than half of many litters of cavalier puppies were born affected by the syndrome. The disorder may be more widespread than previously believed as more owners and veterinarians become aware of its symptoms.
It has been determined to be due to a autosomal recessive gene, a mutation of the FAM83H gene*. As a result, affected puppies are more likely to be found in cases of line breeding or inbreeding on carrier bloodlines.
The reference to a curly or rough coat comes from the unusually curly abnormality of the cavalier's coat which is apparent at birth. However, the puppy also suffers from an extreme version of dry eye*, and as the affected dog matures, it develops a deterioration of the skin which results in seborrhea, consisting of skin inflammation and excessive oiliness. Also, the dog's teeth, gums, and other connective tissues may be adversely affected. The form of dry eye associated with curly coat also is distinctive in that it is of congenital origin.
Other signs include abnormal thickening of the outer layer of the footpads called hyperkeratosis, and abnormal claw formation, called symmetrical lupoid onychodystrophy (SLO).
In 2011, two UK research groups (see below) independently developed DNA swab tests for detecting a recessive gene, the FAM83H gene, which, when mutated, is the cause of curly coat syndrome in the CKCS. Curly coat/dry eye syndrome has been considered to be inherited as a autosomal recessive trait. If a DNA-tested cavalier is found to not have the mutated FAM83H gene, then it is "clear" of curly coat. If the dog is found to have two of the mutated gene, then it is "affected" and has curly coat. If the dog is found to have only one of the mutated gene, then it has been believed to not be affected but is "a carrier".
However, there is some evidence that cavaliers with only one of the mutated FAM83H genes can display symptoms of curly coat and dry eye. In a March 2020 article, a team of Australian researchers reported on a neutered male cavalier first presented at age 15 months and subsequently diagnosed with congenital keratoconjunctivitis sicca and ichthyosiform dermatosis (CKCSID). The dog has been found to have only a single copy of the defective FAM83H gene and was therefore considered to be heterozygous for this genetic defect and presumably only a carrier. The dog's clinical signs have included progressively severe dry eye for which no treatment has been successful. Initially, the condition of the dog's coat has been relatively mild, perhaps reflecting the dog's heterozygous state. No daily treatment has cured any of the dog's conditions, but it has offered some control and relief.
In a May 2012 study of the DNA of 2,803 cavaliers, less than 0.15% were affected with the mutated gene causing curly coat syndrome, but over 8% of cavaliers were found to carry the defective gene. In a June 2012 report of DNA testing of 280 cavaliers, the UK's Animal Health Trust researchers estimate that 10.8% of CKCSs are carriers of curly-coat, and 0.4% are affected. It includes a very severe form of dry eye syndrome, but it is to be distinguished from the much more common form of dry eye in the CKSC breed.
No cases of curly coat syndrome with severe dry eye have been reported in any other breed. Studies have been conducted in the United States, United Kingdom, Australia, Sweden, the Czech Republic, and Iceland. During a two year period recently in Iceland, more than half of many litters of cavalier puppies were born affected by the syndrome. The disorder may be more widespread than previously believed as more owners and veterinarians become aware of its symptoms.
It has been determined to be due to a autosomal recessive gene, a mutation of the FAM83H gene*. As a result, affected puppies are more likely to be found in cases of line breeding or inbreeding on carrier bloodlines.
The reference to a curly or rough coat comes from the unusually curly abnormality of the cavalier's coat which is apparent at birth. However, the puppy also suffers from an extreme version of dry eye*, and as the affected dog matures, it develops a deterioration of the skin which results in seborrhea, consisting of skin inflammation and excessive oiliness. Also, the dog's teeth, gums, and other connective tissues may be adversely affected. The form of dry eye associated with curly coat also is distinctive in that it is of congenital origin.
Other signs include abnormal thickening of the outer layer of the footpads called hyperkeratosis, and abnormal claw formation, called symmetrical lupoid onychodystrophy (SLO).
In 2011, two UK research groups (see below) independently developed DNA swab tests for detecting a recessive gene, the FAM83H gene, which, when mutated, is the cause of curly coat syndrome in the CKCS. Curly coat/dry eye syndrome has been considered to be inherited as a autosomal recessive trait. If a DNA-tested cavalier is found to not have the mutated FAM83H gene, then it is "clear" of curly coat. If the dog is found to have two of the mutated gene, then it is "affected" and has curly coat. If the dog is found to have only one of the mutated gene, then it has been believed to not be affected but is "a carrier".
However, there is some evidence that cavaliers with only one of the mutated FAM83H genes can display symptoms of curly coat and dry eye. In a March 2020 article, a team of Australian researchers reported on a neutered male cavalier first presented at age 15 months and subsequently diagnosed with congenital keratoconjunctivitis sicca and ichthyosiform dermatosis (CKCSID). The dog has been found to have only a single copy of the defective FAM83H gene and was therefore considered to be heterozygous for this genetic defect and presumably only a carrier. The dog's clinical signs have included progressively severe dry eye for which no treatment has been successful. Initially, the condition of the dog's coat has been relatively mild, perhaps reflecting the dog's heterozygous state. No daily treatment has cured any of the dog's conditions, but it has offered some control and relief.
