Dwarfism in dogs

Overview

Dwarfism is an abnormally small body structure, often with skeletal deformity and altered body proportions. Dwarfism can result from abnormalities of the pituitary gland or from genetic mutations.

Pituitary dwarfism

Pituitary dwarfism is the result of inadequate production of growth hormone (GH) by the pituitary gland. This lack of production can be caused by any of the following:

• A lack of development of the pituitary gland
• Cysts within the gland
• Infectious diseases which affect the gland
• Tumors

Dogs appear normal at birth but usually show evidence of failure to grow by two to three months of age. Pituitary dwarf dogs often have normal proportionate sizes to their body structures, they are simply smaller than expected, but may be unable to progress mentally as well as physically.

There are no effective treatments for pituitary dwarfism dogs. Although human growth hormones have been tried, the cost is very high and the results have shown only limited degrees of success. Because so many organs are affected by a lack of growth hormone, normal life spans are not expected.

Pituitary dwarfism is not common, but has occurred in many breeds:

• Alaskan Malamute
• Australian Shepherd
• Collie
• German Shepherd
• Giant Schnauzer
• Labrador Retriever
• Samoyed
• Shih Tzu
• Weimaraner

Genetic dwarfism

Through the centuries, people have selectively bred dogs to retain certain genetic defects or mutations. There are many breeds of dwarf dogs where the characteristics of dwarfism are part of the breed standard. (The name Corgi literally means “dwarf dog” in Welsh.) There are three primary types of genetic dwarfism: chondrodystrophic, achondroplastic and brachiocephalic. Some breeds may exhibit characteristics of more than one kind of dwarfism, for example the Bulldog is both an achondroplastic and a brachiocephalic dwarf.

Chondrodystrophic:  abnormal cartilage growth resulting in shortened legs

• Basset Hound
• Dachshund
• Lhasa Apso
• Pekingese
• Scottish Terrier

Achondroplastic: abnormal cartilage growth resulting in shortened torso with shortened limbs

• Bulldog
• Corgi
• French Bulldog
• Miniature Poodle
• Shar-Pei
• Shetland Sheepdog
• Shih Tzu
• Skye Terrier

Associated health problems:  intervertebral disk disease (IVDD), Osteochondritis Dissecans (OCD), hip dysplasia, vertebral malformations, disk herniation, spina bifida, reproductive problems.

Brachiocephalic: a shortened muzzle compared to the length of the cranium

• Boston Terrier
• Boxer
• Bulldog
• Pekingese
• Pomeranian
• Pug
• Shar-Pei
• Shih Tzu

Associated health problems: breathing problems, air gulping, heat prostration, eye abnormalities, tooth and gum problems, difficulty with normal birthing.

Prevention

Keeping a dwarf breed dog at optimum weight is one of the best preventative measures as being overweight puts stress on vertebrae, leg bones and joints, and even more important for brachiocephalic dogs, heart and lungs. Because their nasal passages are smaller, making it more difficult to circulate sufficient air for cooling, brachiocephalic dogs are more prone to heat discomfort and heat stroke. Keep cool water readily available and take all necessary steps to prevent overheating.

References:

The Association of Veterinarians for Animal Rights, “Guide to Congenital and Heritable Disorders in Dogs.” revised March 2006.  (19 February 2008).

French Bull Dog Club of America, “FRENCH BULLDOG PHYSICAL HEALTH AND CONFORMATION.” (19 February 2008).

Lang, Johann, DECVDI, Martig, Sandra, DVM, et al, “Phenotype of Hereditary Orthopedic Disease--and the Role of Diagnostic Imaging.” (19 February 2008).

Luttgen, Patricia J., DVM. “Canine Intervertebral Disk Disease.” 1993. (19 February 2008).