Warmblood Fragile Foal Syndrome (WFFS) has made it's way to the news recently after top stallion Sternlicht was removed from the 2018 lineup at Hilltop Farm. See their announcement here.
Warmblood Fragile Foal Syndrome (WFFS) is an inherited condition causing thin, fragile skin. Affected foals may be born with skin lesions and an open abdomen and are typically euthanized at birth or within a few days of birth. There is no effective treatment. The condition resembles Ehlers-Danlos syndrome in humans, which has multiple genetic causes. The skin defects resemble those seen in the Hereditary Equine Regional Dermal Asthenia (HERDA), which has a later onset of symptoms. There are also reports of Ehlers-Danlos-like syndromes of unknown origin in a number of breeds. Warmblood Fragile Foal Syndrome is reported only in Warmbloods. The incidence of carriers is approximately 10%.
A foal who is born affected has a 100% euthanasia rate as it cannot survive more than a few hours. Here's a first-hand account of a breeder that experienced this awful fate. (Open in Chrome to translate to English)
Testing your breeding stock is simple and cost-effective ($55) and can help reduce the risk of this happening to your foal. One company (among many) that does this test is Animal Genetics. It is important to understand that a carrier mare can absolutely still have healthy, successful foals with no problem. It only becomes a problem when the mare and stallion are both carriers of the gene and pass it on to the foal.
More information can be found on EquiSec and NCBI.