Dry eye curly coat syndrome (CCS)
Dry eye curly coat syndrome is a congenital disorder that manifests as a rough coat present at birth, with keratoconjunctivitis sicca apparent on eyelid opening at 10–14 days, followed by hyperkeratinisation of footpads and distortion of nails that develops over the next few months. It is caused by a deletion in FAM83H gene, which has an important role in skin development and regulation, in addition to enamel formation. The mutation is recessive and heterozygous dogs do not have a discernable phenotype.
In a report from 2012, of DNA testing of 280 cavaliers, the UK’s Animal Health Trust researchers estimate that 10.8% of Cavalier King Charles Spaniel are carriers of dry eye curly coat syndrome, 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 Cavalier King Charles Spaniel breed. No cases of curly coat syndrome with severe dry eye have been reported in any other breed.
Forman, O.P., Penderis, J., Hartley, C., Hayward, L.J., Ricketts, S.L., and Mellersh, C.S. (2012). Parallel mapping and simultaneous sequencing reveals deletions in BCAN and FAM83H associated with discrete inherited disorders in a domestic dog breed. PLoS Genet. 8, e1002462.