Chondrodysplasia in five Great Pyrenees.

Five disproportionate, short-limbed, short-trunked (dwarf) Great Pyrenees pups were examined. The mode of inheritance was compatible with a simple autosomal recessive trait, and skeletal radiography revealed flaring of the metaphyses of all long bones and the costochondral junctions of the ribs. Vertebral bodies were poorly ossified and short, and had a beak-like extension on the caudal metaphyseal margin. Vertebral body end-plates were thin and concave, and ossification was abnormal. Three of the 5 dogs were deaf, and 1 had testicular atrophy. Ocular examinations did not reveal any abnormalities. Histologic examination of the growth plates revealed disorganized chondrocyte columns, and chondrocytes appeared to have undergone degenerative changes in the zone of chondrocyte proliferation. Transmission electron micrography of growth plate chondrocytes revealed dilated profiles of rough endoplasmic reticulum.