Chondrodysplasia in the Norwegian Elkhound

Dwarfism in the Norwegian Elkhound occurred as a result of a generalized disturbance in endochondral ossification. Radiographic changes included flaring and increased width of the distal metaphyses of the radius and ulna, delayed ossification of the cuboid bones of the carpus, and reduction in length of the vertebral bodies. The zone of chondrocyte proliferation was decreased in width and contained areas of abnormal cell column formation alternated with wide areas of matrix. Chondrocytes in all zones contained one or more inclusions bounded by a smooth discontinuous membrane. The material within the inclusions appeared homogeneous and stained blue-green with Movat's pentachrome and deep blue with alcian blue-periodic acid-Schiff at pH 1.0 and 2.6. The distribution of ruthenium red granules in the matrix frequently revealed poor differentiation into territorial and interterritorial zones. Twenty-four-hour urine samples were negative for glucose, and the glycosaminoglycan excretion pattern was normal.