Warmblood Fragile Foal Syndrome (WFFS) is an inherited systemic connective tissue disorder that is found in Warmblood horses. Skin lacks tensile strength (extreme skin fragility characterized by tearing, ulceration, etc. from contact with normal surroundings). Lesions can occur anywhere on the body but are most noted on pressure points and in addition to skin wounds, lesions are found on the gums and other oral cavity mucous membranes and the perineum. Limb joints are lax and hyperextensible. Fetlocks are the most dramatically affected and affected foals cannot stand normally. Other symptoms may include hydrops, subcutaneous emphysema, hematomas, or premature birth. Affected foals must be euthanized soon after birth.

WFFS is caused by a single mutation in lysyl hydroxylase 1 (LH1) gene. Mutations in LH1 are known to cause a similar disorder in humans known as Ehlers-Danlos Syndrome (EDS). The skin defects resemble, but are much more severe than those seen in the Hereditary Equine Regional Dermal Asthenia (HERDA), which has a later onset of symptoms.