Osteopetrosis in two foals.

This account describes two neonatal foals affected with osteopetrosis. One of these foals, a full term Peruvian Paso, was born alive, was bright and alert but was unable to stand and was euthanized at two days of age. The second foal, an Appaloosa, was also born alive at full term and was blind, weak, uncoordinated and unable to stand. Postmortem examination of both foals revealed generalized osteopetrosis and brachygnathia inferior. The osteopetrosis was characterized by failure of bone remodelling resulting in spicules of mineralized and nonmineralized cartilage covered by osteoid occupying the medullary areas of bones.It was not possible to determine whether this condition has an hereditary basis in horses. Circumstantial evidence suggested that the condition might be inherited in the Peruvian horse.The condition described in foals in this report and in one previous report is compared and contrasted with the disease in cattle. The lesions of osteopetrosis are similar in both species, but slightly less severe in horses.