The human mitochondrial tRNA mutations are associated with a variety of diseases including mitochondrial myopathies. However, it is understood that defects in the mitochondrial DNA (mtDNA) have been associated with these diseases, and studies have been able to assign biochemical defects. One of these defects has to do with the decreased energy available for cell processes. As muscles are stained with Gömöri trichrome, characteristic ragged red fibers are visible under the microscope. This appearance is due to the accumulation of abnormal mitochondria below the plasma membrane of the muscle fiber. These may extend throughout the muscle fiber as the disease severity increases. The mitochondrial aggregates cause the contour of the muscle fiber to become irregular, leading to the "ragged" appearance. Diagnosis
The diagnosis varies from individual to individual. Each is evaluated and diagnosed according to age, clinical phenotype, and pressed inheritance pattern. If the individual has been experiencing myoclonus, the doctor will run a series of genetic studies to determine if it is a mitochondrial disorder.The molecular genetic studies are run to identify the reason of for the mutations underlying the mitochondrial dysfunction. This approach will avoid the need for a muscle biopsy or an exhaustive metabolic evaluation. After sequencing the mitochondrial genomes, four points mutations in the genome can be identified which are associated with MERRF: A8344G, T8356C, G8361A, and G8363A.
Most patients will not exhibit all of these symptoms, but more than one of these symptoms will be present in a patient who has been diagnosed with MERRF disease. Mitochondrial disorders, including MERRF, may present at any age. Due to the multiple symptoms presented by the individual, the severity of the syndrome is very difficult to evaluate. Causes
The cause of MERRF disorder is due to mutations in the mitochondrial genome. This means that it is a pathological variant in mtDNA (mitochondrial DNA) and is transmitted by maternal inheritance. Four point mutations in the genome can be identified that are associated with MERRF: m.A8344G, m.T8356C, m.G8361A, and m.G8363A. The point mutation m.A8344G is most commonly associated with MERRF, in a study published by Paul Jose Lorenzoni from the Department of neurology at University of Panama stated that 80% of the patients with MERRF disease exhibited this point mutation. This point mutation disrupts the mitochondrial gene for tRNA-Lys. This disrupts the synthesis of proteins. The remaining mutations only account for 10% of cases, and the remaining 10% of the patients with MERRF did not have an identifiable mutation in the mitochondrial DNA.Many genes are involved. These genes include:

MT-TK
MT-TL1
MT-TH
MT-TS1
MT-TS2
MT-TFIt involves the following characteristics:

progressive myoclonic epilepsy
"Ragged Red Fibers" - clumps of diseased mitochondria accumulate in the subsarcolemmal region of the muscle fiber and appear as "Ragged Red Fibers" when muscle is stained with modified Gömöri trichrome stain.There is currently no cure for MERRF. Mechanism
The mechanism by which MERRFs syndrome occur is not yet well understood.