The term achondroplasia is used to depict dogs who have bones that do not grow to normal size, causing them to be of a disproportionate short stature leading to what is known as "achondroplastic dwarfism." Achondroplasia is considered a genetic condition, meaning that it's passed down from a generation to another. As much as this disorder may appear problematic up to the point of being crippling in severe cases, achondroplasia is actually encouraged in certain breeds of dogs and is even in their breed standard.
A Lesson in Etymology
To better understand anchondroplasia, let's first start off by taking a look at the history of the word. The "a" in this case is used to mean "not." The word "chondro"comes from the ancient Greek word, khóndros, which means cartilage, and the word "plasia" which means growth.
Put all these words together and you get "a condition where there is no cartilage growth,"or to word it even better, "a condition where there is deficient growth of cartilage." How does this happen though?
A Glimpse at the Process
When a puppy is developing in the womb, its skeleton is made of a flexible material known as hyaline cartilage. Only later, as the puppy develops, its cartilage will transform into bone, through a process known as ossification.
When puppies have a mutation in the gene responsible for converting cartilage to bone, this results in shorter bones, a peculiarity that is readily noticeable soon after birth.
In particular, the effect is most noticeable in the bones of the legs which appear shortened. This is why the term micromelic (meaning short limbs) acondroplasia is often used. On top of appearing shortened, the legs may appear deformed with bowed forelimbs.
Desirable in Certain Breeds...
As mentioned, achondroplasia is acceptable, up to the point of desirable, in certain dogs breeds. In these dog breeds, the achondroplasia isn't fruit of an accidental breeding, but it's actually wanted and purposely encouraged.
In many dog breeds, it's even written in the breed standards. What dog breeds are traditionally classified as being "achondroplastic?" Here is a brief list of some common achondroplastic dog breeds:
- Basset Hounds
- Welsh Corgi
- Skye terrier
"Some breeds of dogs have been bred through the selective encouragement of achondroplasia to achieve short limbs, such as the Dachshund, Skye Terrier and Welsh Corgi." ~Vetary
Undesirable in Others
While achondroplasia is desirable in certain dogs breeds, in some others it's not in the breed standard and it's considered a serious genetic fault.
In this case though, it would be more correct to say that these dog breeds suffer from "chondrodysplasia." In this case, if we look at the etymology, we will notice the the word "chondro" again coming from the ancient Greek word, khóndros, which means cartilage, while the word dysplasia comes from the Ancient Greek dys-, meaning "bad" and plasis, meaning "growth."
Put these words together and you have a bad, or better, "abnormal development of the cartilage."
In what dog breeds is this highly undesirable? In many, but it's considered particularly problematic in Alaskan Malamutes, Scottish deer hounds, Karelian Bear Dogs, Norwegian elk hounds, Great Pyrenees and German shepherds.
The condition in these dogs may not be readily detectable at birth, but signs may manifest later on when the affected dogs show shortened limbs compared to other dogs of the same breed and age. In severe cases, these alterations may cause a crippling effect, but in less severe cases there may be no associated clinical problems.
Fortunately, in the negatively affected breeds, the alterations appear to be due to autosomal recessive inheritance, making them slightly less likely (which is why we don't see it quite as often); whereas, in the dog breeds where it's desirable by standard, it's a matter of dominant inheritance.
"Professor Hannes Lohi's research group at the University of Helsinki and Folkhälsan Research Center has identified a mutation in ITGA10 gene, causing chondrodysplasia in two dog breeds, the Norwegian Elkhound and the Karelian Bear Dog." ~Science News
Advantages of Short Legs
Why would certain dog breeds be purposely bred to have short legs? It turns out, short legs may have provided several benefits in a dog's past as working partners.
For instance, in the dachshund, those short legs and long backs allowed these dogs to easily fit in tight spaces so they could effectively flush out burrowing animals.
In the basset hound, those short legs helped these dogs follow scent easily nose-to-ground (with the long ears helping stir up scent) without getting too far as hunters followed on foot.
In the corgi, those short legs helped these herding dogs effectively duck from kicking hooves, explains Caroline Coile in an article for Vet Street.
- Vet Street, Short on Leg, Long on Love: Learn About The Dwarf Dog Breeds, by Caroline Coile, retrieved from the web on April 6th, 2016.
- The University of Sydney, Faculty of Veterinary Science, Disorder Achondroplasia, retrieved from the web on April 6th, 2016.
- Canine Inherited Disorders Database, Osteochondrodysplasia - skeletal dwarfism, retrieved from the web on April 6th, 2016.
- Helsingin yliopisto (University of Helsinki). "New dwarfism mutation identified in dogs." ScienceDaily. ScienceDaily, 26 September 2013