Genetics of fibrotic myopathy in the German Shepherd Dog
September 19th, 2019
Breed(s): German Shepherd Dog and other breeds affected with fibrotic myopathy
Study Type: DNA samples obtained from blood
Study Location: University of Wisconsin-Madison
Fibrotic myopathy is a specific clinical syndrome with a highly characteristic presentation of profound hindlimb lameness and fibrous contracture of thigh musculature (semitendinosus and gracilis). Diagnosis can be confirmed by physical examination. One or both hindlimbs may be affected. Affected hindlimbs have a shortened stride with a rapid elastic internal rotation of the foot, external rotation of the hock (ankle) and internal rotation of the stifle (knee) during the swing phase. This characteristic gait is caused by altered stifle and hock range of motion. Palpation of the medial thigh reveals a firm taut band extending from the midline of the pelvis to the caudomedial aspect of the stifle. The gracilis muscle is usually more severely affected than the semitendinosus. Palpation of the affected muscles is often painful. Prognosis for affected dogs is very poor. There is no curative treatment and dogs experience permanent disability. Surgical cutting of the fibrotic band in the thigh is unsuccessful as the contracture recurs within a few months. Medical therapy is generally unsuccessful, although, anecdotally, stem cell injections may help mobility over time.
The cause of fibrotic myopathy is not known. Most cases are German Shepherd Dogs, particularly males. Fibrotic myopathy is extremely rare in other breeds, but has been diagnosed in 3 Doberman Pinschers, 2 Belgian Shepherds, 1 St. Bernard, and 1 Old English Sheepdog. This marked breed predisposition suggests the disease is genetic. Fibrotic myopathy is likely a simple (Mendelian) genetic disease in which a single mutation causes the condition.
Further investigation of the genetics of fibrotic myopathy is needed. Data from the Comparative Genetics Laboratory at the University of Wisconsin-Madison suggest that fibrotic myopathy in the German Shepherd Dog is very likely a recessive Mendelian genetic disease, meaning that there is a simple mode of inheritance where dogs with two copies of the mutated gene develop the disease and dogs with only one copy of the mutation are carriers of the disease and are healthy clinically. We are studying the German Shepherd Dog for this work because support from the breed organization and strong engagement with this project by the community of German Shepherd Dog owners.
Our work will advance discovery of the causal genetic variant(s) for fibrotic myopathy. This will not only advance genetic testing for the disease and development of new treatments for affected dogs but will also inform understanding of human muscle injury.
We are currently only able to enroll participants that are able to travel to the University of Wisonsin-Madison School of Veterinary Medicine. Cases must be purebred German Shepherd Dogs with fibrotic myopathy with a pedigree. Although very rare, we also wish to study purebred dogs of other breeds with fibrotic myopathy. Unaffected control dogs must be purebred German Shepherd Dogs with a pedigree over the age of 9 years with no history of fibrotic myopathy or other muscle problems.
Owner’s Responsibilities (Samples and Information to be collected):
All dogs will be recruited with signed consent from their owners. A copy of the pedigree will be collected from each dog recruited to the study. All dogs will have a blood sample drawn for DNA isolation and genome-wide genotyping or whole genome sequencing. For cases we request photographs of the dog and information from clinical examination. Unaffected controls need to be evaluated at the UW School of Veterinary Medicine to verify physical exam findings confirm absence of fibrotic myopathy. Dog age and sex will also be recorded.
Names: Dr. Peter Muir
Facebook: Comparative Genetics Laboratory at UW School of Veterinary Medicine