A recent posting by a UK breeder regarding the condition HCM and PKD in Siberians contained inaccurate information. I responded to this post but it seems the person in question has chosen to ignore my comment.
Here is some information about HCM in cats.
General opinion is that HCM is caused by a DOMINANT gene. SRI have had some anomalies in certain lines and a theory of triggers and suppressors has been put forward, (source conversation with Tom Lundburg). However it is acknoledged that not all pedigree records are correct and that more data has to be gathered and the more people who participate in sharing loses of cats with HCM instead of hiding them, will improve the future for all breeds as this progressive disease is in most populations of pedigree and non pedigree cats.
There are many 'strains' of HCM in the cat populations, I think there are at least three identified in the Siberian to date?
Regarding inbreeding. You will only have a increased number of affected cats if you use a HCM cat.
If one parent have one HCM gene there is a 50/50 chance of passing on the condition.
If both parents have one HCM gene this increases to a 75% chance of offspring being affected
If one cat carries two HCM genes all offpring will be affected.
Remember, these probabilities are for EACH kitten and not a percentage of the litter.
As we have only had a handful of reported cases in the UK it is prudent to monitor your own cats and do follow ups of offspring. I must point out that HCM and its 100s of strains has been in the human population for some time and research is still in its infancy.....
PKD1 in Siberians
Some information about testing your cats from UC Davies
It is likely that PKD1 in Siberians will only manifest itself in cats whose origins include Persian roots or breeds using Persians as permitted outcrosses or where breeders have added these outcrosses to the gene pool. As we do not have reliable documentation about the foundation cats ancestry, or you suspect you cats ancestry may include such cats, a test may be prudent. However, if there is a strain of PKD in Siberians unique to this breed, as yet, no test has been approved. Monitoring of own cats and offspring and any occurances can be monitored and then that line tested and information shared.
It is important for those of us who breed this wonderful cat to be accurate in our publication of infornation. Many readers do not question the sources they read and can be misinformed.
Happily, in six years of owning and breeding Siberians, to date we have no reported cases of HCM/PKD1 cats in our foundation cats onwards :). If this changes I will cetainly let SRI know.