Lethal white syndrome is a genetic disorder that affects horses, particularly those of the Overo coat pattern in certain breeds such as Paint and Pinto horses. Also known as Overo Lethal White Syndrome (OLWS), it is characterized by the absence of pigmentation in the intestines and, in most cases, other areas of the body as well.
When two horses, each carrying a single copy of the OLWS gene, breed, there is a 25% chance that the foal will inherit two copies of the gene, resulting in lethal white syndrome. These affected foals are born with a white coat, which may also be accompanied by blue eyes. However, their lack of pigmentation in the digestive system disrupts the normal functioning of the intestines, leading to health issues such as bowel obstruction and the inability to absorb nutrients.
Lethal white syndrome is so named because affected foals typically do not survive longer than a few days after birth. Despite supportive care, these foals develop severe colic symptoms, fail to pass feces, and rapidly deteriorate due to the intestinal abnormalities associated with the condition. Therefore, euthanasia is often necessary to prevent suffering.
Breeders and horse owners need to be aware of the presence of lethal white syndrome in their horse's lineage and take appropriate measures to prevent unintentional breeding between carriers of the gene. Genetic testing can help identify carriers and prevent the production of affected foals, minimizing the occurrence of this fatal disorder within affected breeds.
