Lethal white foal syndrome (LWO)

Overo lethal white syndrome is an autosomally inherited disease associated with horse breeds that register white coat patterns. The syndrome is associated with a single amino acid substitution at residue 118 on the endothelin-B receptor gene and occurs in white foals born to American paint horses of overo lineage, specifically the frame overo subtype. Affected foals appear normal at birth but fail to pass meconium and develop severe colic as a result of ileus caused by a functional intestinal obstruction. In the absence of veterinary intervention, death ensues, usually within 24 to 48 hours postpartum. Because there is no treatment for this condition, euthanasia is warranted to minimise unnecessary pain and suffering. The Overo coat colour is dominant over other coat colours, but the OLWS disease inherits in an autosomal recessive fashion