Pathology of inherited rickets in Corriedale sheep.

A skeletal disease with features of rickets and simple autosomal recessive inheritance has been discovered in Corriedale sheep in New Zealand. The clinical signs resemble rickets in other species and include decreased growth rate, thoracic lordosis and angular limb deformities. Gross lesions include segmental thickening of physes, growth arrest lines, collapse of subchondral bone of the humeral head, thickened cortices and enthesophytes around distal limb joints. Microscopically, there is persistence of hypertrophic chondrocytes at sites of endochondral ossification, inappropriate and excessive osteoclastic resorption, microfractures and wide, unmineralized osteoid seams lining trabeculae and filling secondary osteons. This study confirms that this skeletal disease of Corriedale sheep is a newly discovered form of inherited rickets and suggests that the genetic defect may be different from inherited forms of rickets described to date in man and animals.