Mitochondrial Myopathy in German Shepherd Dogs

Before we directly drop down to Mitochondrial Myopathy in German Shepherd Dog, let us talk a bit about what is "Mitochondria" and what is "Myopathy" separably.

Mitochondria is the cellular structures in an organism in which energy is produced by oxidation of fuels such as glucose and fat in the form of heat and mechanism i.e. working. Researchers have discovered some of the biochemical defects in the mitochondria. Some of the known mitochondrial diseases in dogs and other organisms occurs due to abnormalities in the mitochondrial DNA.

Myopathy is a neuromuscular disorders which make the muscle fibers dysfunction due to one or more reasons. This consequently results in weakening of muscles, leading to cramping and stiffness of muscles and muscular spasms. Myopathy can be of different types like mitochondrial myopathies, congenital myopathies, muscular dystrophies etc.

Inherited disorders of carnitine metabolism in dogs are amongst the most important causes for mitochondrial myopathy in German Shepherd Dogs and other dog breeds. The mitochondrial disorders in German Shepherds occur due to gene mutations - either nuclear genomes or mutation in mitochondrial DNA. The mutations in mitochondrial DNA in dogs get transmitted by maternal inheritance. Putting this in simple, Mitochondrial myopathies in GSD and in any other canine breeds are caused by genetic mutations, which directly affects the functioning of the electron transport chain (ETC).

Although not in very large numbers, yet a few cases of Mitochondrial Myopathy have been found in canines. The histochemical and ultrastructural findings in case of mitochondrial myopathy in German Shepherd Dog breed have been reported quite infrequently by vets.


Case History: Mitochondrial Myopathy in a German Shepherd Dog

A male German Shepherd Dog of around 36 weeks old had been referred to the Department of Veterinary Clinical Science – Surgery Section, University of Naples for a systematic evaluation of progressive exercise tolerance. The dog had a history of intolerance to exercise, reluctance to move, and spontaneous pain. The symptoms had started showing just a month before the dog was referred to the clinic. The condition had been progressively increasing, showing signs of systemic muscle atrophy, mainly in limb and truncal muscles, accompanied with muscular pain, stiffness in gait, thoracolumbar kyphosis (spinal deformity). The German Shepherd with such a clinical symptoms was exhibiting bunny hopping in hind legs while trying to move fast.

Since the orthopedic and neurologic examinations of the German Shepherd turned out to be unremarkable, his blood samples were collected for hematologic and serologic examination. The report of hematologic examination did not show any abnormalities, while on the other hand the biochemistry revealed an increase in the level of creatine kinase at 37 C (181 U/liter), lactate dehydrogenase (510 U/liter), and aspartate aminotransferase (123.6 U/liter). Moreover, radiographs of stifle region and coxofemoral had been taken. However, no abnormalities could be found in the rediograph report. Muscle biopsies were also taken from the femoral biceps muscle for histopathologic examination.

Organs that get affected by Mitochondrial Myopathy in Dogs

In mitochondrial disorders in dogs, the worst affected organs are the ones that mainly depends on oxidative metabolism (chemical reactions involving oxygen). However, these organs includes brain, skeleton, and heart muscles, sensory organs and kidney. The existence of mildest degree of mitochondrial myopathy in GSD, like any other canine breed will cause mild weakness of muscles, which would be mostly noticed in the arms. There will also be exercise intolerance.

Signs of Mitochondrial Myopathy in canine

German Shepherd Dog - like any other dogs affected with mitochondrial myopathies have severe exercise intolerance that can be consistently demonstrated with even mild exercise. They have stiff, stilted gait, bunny-hopping in the pelvic limbs, reluctance to move, and spontaneous pain. Laboratory tests reveal exercise-induced metabolic acidosis.

Diagnosis of Canine Mitochondrial Myopathy

Diagnosis of mitochondrial myopathies in dog often involves a multifaceted approaches. It requires demonstration of post-exercise plasma lactate and pyruvate concentrations. Light and electron microscopic evaluation of mitochondria of the dog within muscle biopsy sections are also used to diagnose mitochondrial myopathies in canine breeds. Precise characterization is dependent on specialized biochemical tests and molecular studies.

Treatments of Mitochondrial Myopathy in GSD or other canine breeds

Treatments of Mitochondrial Myopathy in GSD or other canine breeds range from treating the symptoms to very specific cause-targeting treatments. The common treatments include administration of antioxidants - especially vitamin E, alternative energy sources - creatine monohydrate, lactate reduction - dichloroacetate and most importantly - exercise training. Exposing the patients to correct type and level of exercise is a particularly very important modality in treating canine Mitochondrial Myopathy.