Dilute coat color with neurological defects (Lavender Foal Syndrome, LFS)

Gene: MYO5A

Transmission: Autosomal, recessive

For an autosomal recessive genetic disease an animal must have two copies of the mutation in question to be at risk of developing the disease. Both parents of an affected animal must be carriers of at least one copy of the mutation. Animals that have only one copy of the mutation are not at risk of developing the disease but are carrier animals that can pass the mutation on to future generations.

Mutation: Deletion, MYO5A gene; c.4249del, p.(Arg1417Ala frame shift STOP 13), chromosome 1.

Breed: Arab

Medical system: Neurologic, dermal (coat colour).

Age of onset of symptoms: At birth.

The syndrome of Dilute coat color with neurological defects, also called Lavender Foal Syndrome, is a fatal, autosomal recessive hereditary disease affecting Thoroughbred Arabian horses, particularly those of Egyptian lineages. Foals affected by the disease exhibit severe neurological disorders from birth, including hyperextension of the back (opisthotonus), involuntary muscle spasms, tetanus, paddling leg movements and tetanic seizures, and involuntary eye movements (nystagmus). Foals have a characteristic diluted coat coloration, ranging from pale grey to lavender, hence the name Lavender Foal Syndrome. Affected foals are generally unable to stand and are usually euthanized within hours of birth. DNA studies identified a mutation in the MYO5A gene as the cause of the disease. The MYO5A gene codes for a motor protein involved in the transport of vesicles along actin filaments within the cell. This is particularly important for neurons, for neurotransmitter transport trafficking within axons and synaptic vesicles, and also for the transport of melanosomes within melanocytes.

Veterinarians and breeders of Arab horses should be aware of this disease. DNA tests should be performed to identify carrier animals and selective breeding should be performed to eliminate the disease and the mutation from the breed.

References:

OMIA link: [1501-9796]

AbouEl Ela NH, El Araby IE, Saleh AA, et al. (2023) Evidence for origin of lavender foal syndrome among Egyptian Arabian horses in Egypt. Equine Vet J 55:487-493. [pm/35665534]

Gabreski NA, Haase B, Armstrong, CD, et al. (2012) Investigation of allele frequencies for Lavender foal syndrome in the horse. Anim Genet 43:650. [pm/22497275]

Brooks SA, Gabreski N, Miller D, et al. (2010) Whole-genome SNP association in the horse: identification of a deletion in myosin Va responsible for Lavender Foal Syndrome. PLoS Genet 6:e1000909. [pm/20419149]

Page P, Parker R, Harper C, et al. (2006) Clinical, clinicopathologic, postmortem examination findings and familial history of 3 Arabians with lavender foal syndrome. J Vet Intern Med 20:1491-4. [pm/17186871]

Contributed by: Camélia Gaudreau and Gabrielle Perot, Class of 2029, Faculté de médecine vétérinaire, Université de Montréal. (Translation DWS)