Myotonic Myopathy In Miniature Schnauzers

Written by: Dr. Martin DeForest & Donna Ralph

In the past few years, a new inherited condition has come to light in our breed. Our first exposures to this devastating condition was in a litter sired by Am. Can. Bda Ch Blythewood From The Terrace, ("Terry" owned by Dr. Martin DeForest) from a privately owned bitch. The owner reported that three of the four puppies appeared to be somewhat unusual in their manner of walking. When I first had the opportunity to observe them, they were approximately 6 weeks old. While they did look mildly uncoordinated, I attributed this to the young age and the smooth surface that they were walking on. The owner also reported that they seemed to make respiratory noises that were louder than usual. In addition, she remarked that they were very sloppy eaters and attempts to drink water left large amounts of water on the floor surrounding the bowl.

Approximately two weeks later, I had the opportunity to examine them once again. I was amazed at how the condition had progressed in such a short period of time. Three of the puppies had markedly increased upper respiratory sounds which were distinctly raspy in nature. These puppies had decreased ability to move their tongue and the tongue did not fully withdraw into the mouth. Consequently, a small amount of tongue tip protruded at all times. The three affected puppies displayed varying decreased mobility and seemed to show great difficulty in rising from a lying position. They exhibited a very stiff gait which was especially evident in the rear limbs. When they attempted to run, they would often adopt a "bunny hop" gait. They displayed a reduced ability to balance and would often fall over. While three of the four were obviously affected by the disorder, some were more so than others.

The symptoms progressed as the puppies grew older. These were characterized by a decreased gag reflex, high pitched bark, and a stiff-legged gait. This improved marginally with exercise. Skeletal muscles, though enlarged, were painless on palpation and the mandible (upper jaw] assumed a more beak-shaped appearance. Following compression, using a thumb, the tongue remained dimpled for more than 30 seconds.

Subsequently, a half sister to the dam of this litter, was bred to a dog related to Terry and produced three puppies. By approximately 7 weeks of age, two of these puppies were displaying similar signs.

Puppies from the first litter and a second litter sired by Terry were autopsied at veterinary teaching hospitals. Results were consistent with the findings of researchers C. H. Vite et al at the School of Veterinary Medicine and School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania. Their findings suggest abnormal chloride or sodium transport across muscle membranes which characterizes this disorder as a biochemical problem. This specific disease of muscles appears to be found only in our breed and is now known medically as Myotonia or Myotonic Myopathy.

An autosomal recessive mode of inheritance has been postulated and all affected individuals to date are direct descendants of one outstanding living American stud. A colony of Miniature Schnauzers with Myotonic Myopathy has been established at the University of Pennsylvania in order to further the study of this disorder. In addition, the staff of Michigan State University have embarked on a genetic study to find a DNA marker in hopes of identifying carrier animals. Michigan State University will be submitting a proposal to the American Kennel Club Research Fund. For further information on this aspect, kindly contact Carol J. Somers, Zomerhof Kennels, Fax. #616-629-9427, E-Mail

In over 30 years as a breeder and over 20 years as a practicing veterinarian, I have not seen a more devastating disease to affect our breed or any other. Your cooperation is urgently needed.

Dr. Martin DeForest
Cherrylane Reg.

Donna Ralph
Moondreamer Perm Reg.

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