What is Myotonia Congenita?
Myotonia congenita is an inherited muscular disease found in Miniature Schnauzers. It is characterized by the delay of skeletal muscle relaxation following the cessation of a voluntary activity. The delay in skeletal muscle relaxation is not accompanied by pain or cramping.

Affected animals have significant excessive growth of the muscles (muscle hypertrophy). They also have a stiff, stilted gait that improves with exercise. Difficulty in swallowing, excessive salivation and an abnormal bark are often present. All affected Miniature Schnauzers examined so far at the University of Pennsylvania also have overshot upper jaws (maxilla) and abnormal dentition, but that is not typical of myotonia in other breeds of dogs and in other species.

Click here for information on treatment.

The DNA Test
The DNA test for myotonia congenita in Miniature Schnauzers is now available from the Josephine Deubler Genetic Disease Testing Laboratory of the University of Pennsylvania School of Veterinary Medicine. Dr. Urs Giger, head of the Laboratory, has advised us that the test is definitive because a specific defect has been identified in the DNA sequence of affected and carrier animals. The Laboratory will be accepting blood samples beginning immediately. The cost for testing is $75 U.S. per sample. Master Card and Visa credit cards are accepted.

Instructions For Submitting Samples

1. The blood must be drawn by your veterinarian. Your veterinarian will need to draw 1 to 2 milliliters of blood and store it in a EDTA tube (lavender colored top).
   
2. Complete and enclose a Submission Form for each sample. Be sure the name on the tube matches the name on the Submission Form. Click here to download the Myotinia Submission Form in Adobe Acrobat (pdf) format. (You will need Adobe Acrobat Reader to view and print the Submission Form. If you do not have a copy, you may obtain one free from Adobe’s web site, http://www.adobe.com/prodindex/acrobat/readstep.html.)
   
3. Please label each tube with your name and address and the name of the animal whose blood is contained in the tube. The tube(s) must be inserted in a small safe container to prevent breakage and shipped to University of Pennsylvania. (Most vets have styrofoam tube containers.) Alternatively, pack each tube in sufficient cushioning material and a sealed Ziploc bag. Penn says that it is not necessary to pack the tube(s) with ice, but it may be wise to do so if shipping during the hot summer months. University of Pennsylvania recommends Second Day delivery – Express Mail, $2.95 for shipments from within the U.S. Express mail is cheaper, but if you want assurance that your samples were received, send them by FedEx, UPS, or some other method of shipping that allows tracking through the shipper. Do not call the Deubler Laboratory to see if samples have been received.
   
4. If you are testing litters, please label each tube carefully with a name or code for each animal that you can recognize. Keep in mind, though, that the certificate of results will show the name or identification you provide. Thus, if you test animals who have not yet been registered, you may need to test them again if you later need a certificate showing the registered name (e.g., if you offer the animal at stud and someone asks for proof that he has been tested as clear).
   
5. Persons submitting samples from outside the U.S. must also enclose a “Proforma Invoice”. Click here for further details.

If you have questions about submitting samples, please call or e-mail Vera Potiker, This e-mail address is being protected from spam bots, you need JavaScript enabled to view it , (909) 780-6284 , rather than bothering the lab personnel.

Who Should Have Their Dogs Tested?
There is no way of predicting, without testing, which animals are carriers; nor can we even say that animals from certain bloodlines are less likely to be carriers than those from other bloodlines. None of these questions can be answered until a significant number of Miniature Schnauzers have been tested

With this information, testing your Miniature Schnauzer for myotonia is added to your considerations before deciding to breed. Each animal need be tested only once, not every time it is bred and you might decide not to test animals that are healthy and will not be bred again or at all. Dr. Giger recommends testing any animals with suspicious clinical signs in order to confirm a clinical diagnosis of myotonia congenita.

All offspring arising from the mating of animals that have both tested clear should be clear. Nonetheless, the Deubler Laboratory recommends testing every breeding animal – even if both parents tested clear – until there has been more real-world experience with the DNA test.

So far, the incidence of myotonia congenita has been fairly low. If we act before it becomes more prevalent and much harder to eliminate from the breed, the $75 cost will be some of the cheapest insurance we can find to avoid future heartbreak.

The AMSC cannot require that members test – but individual members may decline to buy or breed to untested animals. You may request a copy of the test certificate for any stud dog you are planning to use and you may request a copy of the test certificates for any animal you are planning to buy for show or breeding purposes.

You might also suggest prospective puppy buyers to ask about test certificates of the parents. If enough puppy buyers become knowledgeable and ask questions, maybe they can encourage the puppy mills and backyard breeders to get their stock tested too.

Breeding Considerations
Based on the present understanding of the mode of inheritance:

1. Breeding an affected to an affected will produce affected offspring who are all affected.
2. Breeding a carrier to an affected or to another carrier yields an unacceptably high risk of producing affected offspring.
3. Breeding an affected or a carrier to a clear does not risk producing affected offspring, but does carry significant risk of spreading the mutated gene to further generations. All offspring that are to be used for breeding would have to be tested to be sure that they do not carry the mutated gene.

The only question of practical importance is whether carriers should be bred to clears. If a carrier has desirable traits that the breeder wishes to preserve in future generations – and which are not available from a clear animal – the carrier should be bred only to a known clear animal. All offspring considered for breeding should be then tested as some of them will likely be carriers.

University of Pennsylvania will not release test results for specific animals to anyone other than the owners or submitting veterinarians; but Dr. Giger has advised us that they will provide statistical results on the frequency of carriers and affecteds to the AMSC once a sufficient number of animals have been tested. We will report on those results as they become available, and may make additional recommendations as warranted based on the advice of the experts.

Contributions Requested For the Deubler Laboratory
Dr. Giger has asked the AMSC and/or Miniature Schnauzer breeders to contribute funds to the Deubler Laboratory to defray at least some of the expenses it has incurred in finding the mutated gene and in developing the DNA test. Dr. Giger told us that the Deubler Laboratory incurred extra expense to complete the work as quickly as possible because the AMSC urged them to do so. More importantly, the Deubler Laboratory will not be making a profit on the DNA tests as they are only charging $75 per test.

Dr. Giger’s request is more than reasonable. The University of Pennsylvania did all of the work with no financial help from Miniature Schnauzer breeders. Most of the time when we fund research, we are asked to do so in the hope that something useful will result. Here, University of Pennsylvania has actually delivered the goods before asking us to pay anything. Also, University of Pennsylvania is pricing the test at considerably less than the $250 to $400 a test several of the other University-affiliated labs, such as Cornell’s and Michigan’s, have charged for similar DNA tests for other disorders.

In order to make the contributions tax-deductible for those paying U.S. income tax, please make your checks payable to the “University of Pennsylvania”. Please mark the memo section of the check “Deubler Laboratory – Miniature Schnauzers” and please mail the checks to Vera Potiker, 7607 Whitegate Avenue, Riverside, CA 92506-5441, so that we can keep track of the donations and make sure that Miniature Schnauzer breeders get credit for the contributions. All donations will be acknowledged in AMSCOPE. University of Pennsylvania will provide the receipts.

This article was prepared by the Health Committee of the AMSC based on information received from Dr. Charles Vite and Dr. Urs Giger. Drs. Giger and Vite reviewed the information contained herein for accuracy.

Urs Giger, PD Dr.med.vet. FVH, is a Diplomate of the ACVIM and of the ECVIM (Internal Medicine), and is the Charlotte Newton Sheppard Professor of Medicine, and Chief, Section of Medical Genetics, at the School of Veterinary Medicine of the University of Pennsylvania. Charles H. Vite, DVM, is a Diplomate of the ACVIM in Neurology and practices at the School of Veterinary Medicine of the University of Pennsylvania.

Copyright, American Miniature Schnauzer Club, Inc., 2000.

Last Updated: Wednesday, December 20, 2000