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Category: Dogs

Mitochondrial Disorders (Study Closed)
October 18, 2004 (published)
Dr. Paula M. Pattengale
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Dr. Vamsi Mootha at MIT is looking for dogs or other species with mitochondrial disorders. His research with mitochondrial disorders has now reached a point where he wants to work with animal models. He will work with the veterinarian and the owner of the pet.

Mitochondrial disorders in humans were first recognized in a case study published in 1986. Since then numerous diseases have been attributed to mitochondrial dysfunction. Most mutations are genetic in origin although some toxins have been incriminated in altered mitochondrial function. The mutations are maternally transmitted with equal distribution between male and female offspring. While present from birth, diagnosis may not be made until a patient reaches adulthood and frequent misdiagnoses are made due to the unfamiliarity of the medical profession with this group of diseases.

These are multisystemic diseases. The severity of tissue involvement depends on the percentage heteroplasmy of the affected tissues and the energy requirements of each tissue. Heteroplasmy also affects lifespan and clinical signs. Hence neurological signs are often noted with decreased or absent reflexes, neuropathy, diminished hearing and vision, vestibular changes, epilepsy and even paralysis. Muscle changes vary from weakness and lack of stamina to myoclonus and cardiomyopathies. Smooth muscle dysfunction is frequently noted with delayed gastric emptying, gastric reflux, chronic constipation, bloating and intermittent bouts of diarrhea. There may be endocrine disorders including hypothyroidism and diabetes mellitus. Often there are multiple endocrine disorders in the same individual. Dysautonomia can be present with alterations in blood pressure and apnea often noted.

Depending on the specific mutation within the mitochondria, various laboratory abnormalities will be present. In the case of MELAS (mitochondrial encephalomyopathy, lactic acidosis, stroke-like episodes), the a3243g mtDNA mutation, lactic acidosis is a prominent finding. Fresh muscle biopsy is used for definitive diagnosis with a limited number of laboratories running the necessary molecular tests to identify specific mutations. Histopathologically, ragged red fibers with excessive mitochondria are noted on examination in MNGIE, another mitochondrial disease. MRI reveals lesions similar to those of multiple sclerosis but with an atypical distribution.

Treatment is symptomatic only. At this time there are anecdotal cases of improvement with the administration of antioxidants and Coenzyme Q 10, L-carnitine, and alpha lipoic acid. This is a chronic, progressive and ultimately fatal disease.

For additional information refer to (The foundation also provides grants for mito research.)

A few cases of mitochondrial diseases have been reported in dogs identified at necropsy. The goal now is to identify naturally occurring lineages of animals with mitochondrial diseases to act as models for human mitochondrial diseases.

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Revised 10/26/04

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