When we researched CKC Spaniels, we were made aware this breed has a number of serious hereditary health issues like Heart and Eye disease. We occasionally saw the term SM. It did not register. We only focused on ensuring the puppies were Heart and Eye clear.
The following is a very brief and simplified overview of SM/CM. It will provide links and contacts of where to obtain proper help and advice to ensure your dog does not suffer needlessly.
There can be varying degrees of this disease. For some dogs it can be traumatic and painful. For others it can be managed with the right medication and care.
Further on in this book, there are illustrations of how both Molly (SM) and Dougall (CM) are both coping and living happy and contented lives.