Breed genetic panel for the Cavalier King Charles Spaniel grouping two well-characterised recessive hereditary conditions: « episodic falling » (EF, hypertonic episodes induced by exercise/emotion) and « dry eye curly coat » syndrome (CCS, congenital keratoconjunctivitis sicca + curly coat + ichthyosis/scaling + flaking). Both have been associated with different variants and often co-segregate in the breed, so they are offered combined.

Cavalier King Charles Spaniel. Carrier frequency is not systematically published in the accessible literature (limited data). Breed screening before breeding is recommended.

- EF: episodes of rigidity, hypertonicity and collapse induced by exercise or excitement, with consciousness preserved
- EF: rigid, high-stepping gait, tense facial expressions, myotonia-like
- CCS: dry eye (keratoconjunctivitis sicca) with mucopurulent discharge and keratitis
- CCS: curly/woolly coat, ichthyosis and flaking, hyperkeratotic paw pads
- CCS: congenital or juvenile onset

EF was described clinically and electrophysiologically in the CKCS in the 1990s. Forman and colleagues (2012, PLoS Genetics) identified deletions in BCAN (brevican), the cause of EF, and in FAM83H, the cause of CCS syndrome; in both cases they are deletions, not missense variants. Both conditions are now included in breed panels and co-segregate due to a founder effect in the CKCS.

- Genotype breeding animals for EF (BCAN) and CCS (FAM83H) before mating
- Do not mate two carriers for the same variant
- A carrier may be mated to a clear animal and the offspring intended for breeding must be tested
- After a confirmed clinical case, do not repeat the parental mating and inform the buyer
- CCS is not merely a cosmetic problem: dry eye affects quality of life and must be treated

EF must be distinguished from myelinopathies, idiopathic epilepsy, myasthenia and congenital myopathies. The episodic hypertonic presentation with preserved consciousness is suggestive. CCS requires ophthalmic assessment (Schirmer test, fluorescein staining) and management of the tear film; in severe forms surgery may be considered. The coexistence of EF+CCS in the same animal homozygous for both is possible and complicates management.

1. Forman OP et al. 2012. Parallel mapping and simultaneous sequencing reveals deletions in BCAN and FAM83H associated with discrete inherited disorders in a domestic dog breed. PLoS Genet. PMID: 22253609
2. Gill JL et al. 2012. A canine BCAN microdeletion associated with episodic falling syndrome. Neurobiol Dis. PMID: 21821125
3. Urkasemsin G et al. 2014. Canine paroxysmal movement disorders. Vet Clin North Am Small Anim Pract. PMID: 25441627
4. OMIA:001592-9615 (Episodic falling, BCAN) y OMIA:001683-9615 (queratoconjuntivitis sicca congénita e ictiosis, FAM83H).