Lavender foal syndrome (LFS) is an inherited lethal coat color dilution found primarily in Arabian horses that is characterized by a dilute lavender, pale pink, or silver coat accompanied by severe neurological abnormalities.
Phenotype: Lavender foal syndrome is characterized by seizures, severe hyperextension of limbs, neck, and back, stiff paddling leg movements, involuntary eye movement, and inability to stand or sit upright. LFS foals are typically born with a telltale dilute coat color described as lavender, pale pink, or silver.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal/Unaffected, LFS = Lavender foal syndrome
Breeds appropriate for testing: Arabian, Arabian crosses
Explanation of Results:
Horses with N/N genotype will not have lavender foal syndrome and cannot transmit this lavender foal syndrome variant to their offspring.
Horses with N/LFS genotype will not be affected by lavender foal syndrome, but are carriers. They may transmit this lavender foal syndrome variant to 50% of their offspring. Matings between two carriers result in a 25% chance of producing a lavender foal syndrome-affected foal.
Horses with LFS/LFS genotype will have lavender foal syndrome, a fatal condition.
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Lavender foal syndrome (LFS), also known as coat color dilution lethal, is a fatal autosomal recessive condition of Arabian horses. LFS is found primarily in horses with Egyptian bloodlines but has also been reported in other Arabian breeding groups. Characteristic signs of LFS include seizures, severe hyperextension of limbs, neck, and back (opisthotonos), stiff paddling leg movements, involuntary eye movement (nystagmus), and inability to stand or sit upright. LFS foals are typically born with a telltale dilute coat color described as lavender, pale pink, or silver, hence the name of the disease. Because birthing of LFS foals is often difficult, the signs can be misinterpreted as resulting from oxygen deprivation during delivery or from a spinal cord injury. LFS foals may have a strong suckle reflex and may be bottle fed, but the disease is untreatable and will not improve. Foals will die or have to be euthanized shortly after birth.
The genetic defect results from a mutation in the MYO5A gene (g.138235715del) that causes neurological dysfunction in newborn foals. This mutation affects the function of melanocytes and neurons in foals and results in both the coat color dilution and neurological defects. Researchers investigating the prevalence of LFS found the frequency of the affected allele to be about 1.6% in non-Egyptian Arabian horses and about 10.3% in Arabian horses of Egyptian descent.
Testing for LFS can assist veterinarians in making the correct diagnosis and owners in identifying affected and carrier horses. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing affected foals. Matings between two LFS carriers have a 25% percent chance of producing LFS affected foals.
Brooks, S. A., Gabreski, N., Miller, D., Brisbin, A., Brown, H. E., Streeter, C., Mezey, J., Cook, D., & Antczak, D. F. (2010). Whole-Genome SNP Association in the Horse: Identification of a Deletion in Myosin Va Responsible for Lavender Foal Syndrome. PLoS Genetics, 6(4). doi: 10.1371/journal.pgen.1000909
Gabreski, N. A., Haase, B., Armstrong, C. D., Distl, O., & Brooks, S. A. (2012). Investigation of allele frequencies for Lavender foal syndrome in the horse. Animal Genetics, 43(5), 650-650. doi: 10.1111/j.1365-2052.2011.02305.x
The LFS test is performed under license from Cornell University.