The gene was found and it is a DOMINANT gene, NOT an autosomal recessive. This means if one parent has the gene, he/she can and will pass it on to some of the offspring. Both parents do not have to carry the gene, just one!
Being one of the breeders that has been actively breeding away from CD for many years now, by NEVER breeding a Havanese that displays CD, I and others have learned that it appears to act like some sort of AR gene, but not quite as simply. Even being 3 generations out on both sides of the pedigree, has proven to occasionally produce a puppy with CD. It's frustrating and discouraging, but I feel very hopeful for a brighter future now with the Havana Silk Dog Association of America bringing to the table for HSD dogs, a very strict criteria through their unique registry which requires an evaluation process by certified HSD evaluators, to rule out any CD, before being allowed in a breeding program.
Not surprisingly, since breeding away from the bowed, heavier boned (CD) Havanese, we are not seeing cataracts, liver problems or premature aging of the hearts in our Silk Dogs!
Over the years, I've had many people call me or email who did not buy their Havanese from me but were worried and shocked, when they bathed their young dog, to realize one of both front legs was bowed. As I mention below, all CD is not a death sentence and many CD dogs can live a pretty healthy normal life, but it appears that many of their life expentences are shortened somewhat. Still, the years that you do love and own them can be good ones, so don't panic.
If you are a person who is looking into buying a Havanese (or an Havana Silk Dog) in the future please do your homework and ask even demand to see soaped picture of the parents forelegs before you put any money down on a puppy or consider purchasing it. Even this is not a 100% guarantee, but it sure ups your odds of getting a healthier pup.
Chondrodysplasia is generally considered to have a genetic basis.
There are many symptoms associated with chondrodysplasia- the skeletal/orthopedic
problems that characterize it, ocular problems (cataracts, retinal abnormalities,
lens luxation (detached lens), microphthalmia (small eyes), nystagmus (involuntary,
rhythmical, repeated oscillations of one or both eyes) and glaucoma. Other symptoms
are various skin problems including patchy alopecia (hair loss), abnormalities
of the skull and trachea, short necks, hearing loss, and patellar (knee) luxation are
all known to be associated with the disease. Some forms of CD are also associated with
various organ abnormalities, primarily the heart, liver and kidneys.
Chondrodysplasia is usually part of a syndrome; in other words, all dogs may not have all the
associated symptoms, but will probably have more than one symptom.
Symptoms range from very mild (slight asymmetry or bowing of the legs)
to severe, which is pretty easily recognizable, and is often associated with multiple health
problems. Severely affected dogs may require extensive (and expensive) orthopedic surgery to correct various
skeletal problems, usually before a year of age.
The important thing to remember is that Chondrodysplasia, with few exceptions is a symptom of a genetic disease. It is a metabolic disorder, much like Type I diabetes - a faulty gene causes a disruption in a metabolic pathway necessary for normal health.
Chondrodysplasia has been identified by veterinarians and orthopedic specialists in many
Havanese, in fact, it is all too common in this breed, whose Breed Standard has ALWAYS
called for straight legs. (In fact, the earliest HCA Standard specifically faulted bowlegs.)
In many breeds, chondrodysplasia is part of their standard, and is critical to Breed Type.
Dachshunds, Corgis, and Bassett hounds are some examples of CD breeds,
but this is not true of the Havanese. The earliest HCA Standard written for the
Havanese breed in this country ( January, 1982) described a dog that was slightly longer
than tall, with straight forelegs, standing no more than 10 1/2 inches at the shoulder, and
weighing no more than 13 lbs. Compare that to the Cardigan Welsh Corgi, whose standard
calls for a curved forearm, a height range from 10 1/2 to 12 1/2 inches at the shoulder,
and a weight range from 25 to 38 pounds. The Corgi is a CD breed; the Havanese is not.
Of concern to Havanese breeders and potential owners should be the fact that, to date, all of the
early-onset blinding cataracts, and nearly all of the other serious health problems reported
in Havanese within the past few years, have been in dogs that also exhibit the symptoms of CD.
Because of the apparent connection between cataracts and chondrodysplasia, HEART, in
association with Dr Keith Murphy and his team at Texas A&M, has supported
research into this disease. Page 2 on Chondrodysplasia