Dermoid sinus is a condition that occurs in several breeds but is most common in the Rhodesian Ridgeback, the Shih Tzu and the Boxer. The breed most highly affected by the condition is the Rhodesian Ridgeback, although it may also show up in mixed breeds with a history of Rhodesian Ridgeback breeding in their line. Dermoid sinus is caused by a recessive gene, which means that both the male and female must carry the gene for the condition in order for the offspring to have the condition. If any puppy in the litter is born with the condition, breeders know that both parents are carriers of the gene, even if they do not have any signs of dermoid sinus themselves. These dogs should not be bred again to prevent the possibility of producing puppies with the condition and stop puppies being born that will be carriers. It is important to note that not only should the affected puppy be neutered or spayed, but all littermates have the likelihood of being carriers so they should also be spayed or neutered and not allowed to be used in breeding programs.
Not all forms of dermoid sinus are serious or debilitating. The condition is caused when the puppies are developing as embryos and the spinal column that develops from a neural tube does not part from the skin, resulting in a bulge or cyst along the back. If it is open, the cyst or bulge is still attached to the spinal column, however if it is what is known as a blind sac there is no actual connection, just the physical cyst. In these cases the dog will have a small or large lump on the back that simply needs to be observed for any signs of swelling or any signs of drainage. Changes in the physical shape or size of the cyst need to be immediately checked by a vet.
Since puppies are born with the condition symptoms may be evident very early or they may not become pronounced until the puppy starts to grow. What owners should watch for are lumps or cysts along the back that are draining or have opening or holes or depressions in the center of the cysts. Often this is hard to see because of the amount of hair, but the discharge from the cyst will be noticeable on the coat. If the cysts are open there are a high percentage of puppies that will develop meningitis, which is an inflammation of the covering of the spinal cord and the brain, or myelitis, which is an inflammation of the spinal cord itself. Once that happens, signs of stiffness of the back, inability to coordinate movement, neurological impairments and fever will be noted.
Treatment includes x-ray and testing to determine the amount of connection between the dermoid sinus cyst and the spinal cord and surgical closure of the connection. In addition aggressive treatment of the inflammation of the brain or spinal cord is also essential in minimizing long term effects of the condition. Typically if the dog or puppy has started to show signs of neurological impairment the treatment cannot reverse the symptoms, so owners need to start treatment as early as possible to prevent long term disability for the puppy or dog.