Chondrodysplasia in five Great Pyrenees

Area of Science:

• Veterinary Genetics
• Canine Pathology
• Skeletal Dysplasia

Background:

• Dwarfism in Great Pyrenees dogs presents as disproportionate limb and trunk shortening.
• Previous understanding of the genetic basis and specific skeletal abnormalities was limited.

Purpose of the Study:

• To investigate the inheritance pattern and detailed skeletal and cellular pathology of dwarfism in Great Pyrenees pups.
• To characterize the ultrastructural changes in growth plate chondrocytes.

Main Methods:

• Examination of five affected Great Pyrenees puppies.
• Skeletal radiography and radiography of costochondral junctions.
• Histological examination of growth plates.
• Transmission electron microscopy of chondrocytes.

Main Results:

• Inheritance pattern consistent with a simple autosomal recessive trait.
• Radiographic findings included metaphyseal flaring, poorly ossified vertebral bodies with beak-like extensions, and abnormal end-plates.
• Histology revealed disorganized chondrocyte columns and degenerative changes; electron microscopy showed dilated rough endoplasmic reticulum in chondrocytes.
• Associated findings included deafness in three pups and testicular atrophy in one.

Conclusions:

• The dwarfism is likely due to a simple autosomal recessive mutation affecting skeletal development.
• Chondrocyte degeneration and abnormal endoplasmic reticulum function are implicated in the pathogenesis of this skeletal dysplasia.
• The condition may also be associated with other congenital defects like deafness and testicular abnormalities.