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"Warmblood" Fragile Foal Syndrome

"Warmblood" Fragile Foal Syndrome (wffs or ffs)


Gene or region:  PLOD1

Reference allele: C

Mutant allele: T

Affected Breeds: Warmbloods and other breeds

Research Confidence:                         Moderate confidence, mutations in same gene cause same condition in other species

wffs/n = Carrier; one allele detected.  Currently no known affect.  Can pass one wffs allele to 50% of any offspring.

wffs/wffs = Affected;  Horse may be aborted, stillborn or born with lesions and thin skin resulting in death.

n/n or negative = Non-carrier, non-affected; unable to pass wffs to any offspring.


What it does:  


Warmblood fragile foal syndrome is a connective tissue disorder resulting in joint laxity and extremely thin skin that is only loosely connected to the body. The skin is easily torn, resulting in lacerations, hematomas, and seromas across the foal. Affected foals are euthanized shortly after birth. As Warmblood fragile foal syndrome is a recessive disorder, horses must inherit two copies (wffs/wffs) to show the disease. Horses with only one allele (WFFS/N) are known as carriers due to their ability to produce affected offspring.


PLOD1 is an enzyme involved in collagen synthesis. Mutations in mice and humans result in similar connective tissue disorders. The mutation observed in horses alters an amino acid, likely disrupting the function of the encoded protein.



Monthoux C et al., “Skin malformations in a neonatal foal tested homozygous positive for Warmblood Fragile Foal Syndrome.” (2015) BMC Vet Res. 11: 12.  PMID: 25637337

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