mitochondrial disease

Her daughter, Brittany, now 14, was a source of great strength when she was diagnosed with breast cancer in June 2006 and underwent a mastectomy and then a hysterectomy.

Mitochondrial disease
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Mitochondrial disease
Classification & external resources
Simplified structure of a typical mitochondrion
DiseasesDB 28840
MeSH D028361
Mitochondrial diseases are a group of disorders relating to the mitochondria, the organelles that are the "powerhouses" of the eukaryotic cells that comprise higher-order lifeforms (including humans). The mitochondria convert the energy of food molecules into the ATP that powers most cell functions.

Mitochondrial diseases comprise those disorders that in one way or another affect the function of the mitochondria and/or are due to mitochondrial DNA. Mitochondrial diseases take on unique characteristics both because of the way the diseases are often inherited and because mitochondria are so critical to cell function. The subclass of these diseases that have neuromuscular disease symptoms are often referred to as a mitochondrial myopathy.

Contents
1 Mitochondrial inheritance
2 Defects and symptoms
3 Types
4 Treatment
5 References
6 External links



[edit] Mitochondrial inheritance
Mitochondrial inheritance behaves differently from autosomal and sex-linked inheritance. Nuclear DNA has two copies per cell (except for sperm and egg cells). One copy is inherited from the father and the other from the mother. Mitochondria, however, contain their own DNA, and contain typically from five to ten copies (see Heteroplasmy), all inherited from the mother (for more detailed inheritance patterns, see Human mitochondrial genetics). When mitochondria divide, the copies of DNA present are divided randomly between the two new mitochondria, and then those new mitochondria make more copies. As a result, if only a few of the DNA copies inherited from the mother are defective, mitochondrial division may cause most of the defective copies to end up in just one of the new mitochondria. Mitochondrial disease begins to become apparent once the number of affected mitochondria reaches a certain level; this phenomenon is called 'threshold expression'.

Not all of the enzymes and other components necessary for proper mitochondrial function are encoded in the mitochondrial DNA. Most mitochondrial function is controlled by nuclear DNA instead.

Mutations to mitochondrial DNA occur frequently, due to the lack of the error checking capability that nuclear DNA has. This means that mitochondrial disorders often occur spontaneously and relatively often. Sometimes the enzymes that control mitochondrial DNA duplication (and which are encoded for by genes in the nuclear DNA) are defective, causing mitochondrial DNA mutations to occur at a rapid rate.


[edit] Defects and symptoms
The effects of mitochondrial disease can be quite varied. Since the distribution of defective DNA may vary from organ to organ within the body, the mutation that in one person may cause liver disease might in another person cause a brain disorder. In addition, the severity of the defect may be great or small. Some minor defects cause only "exercise intolerance", with no serious illness or disability. Other defects can more severely affect the operation of the mitochondria and can cause severe body-wide impacts.

As a general rule, mitochondrial diseases are worst when the defective mitochondria are present in the muscles, cerebrum, or nerves,[1] because these are the most energy-hungry cells of the body.

However, even though mitochondrial disease varies greatly in presentation from person to person, several major categories of the disease have been defined, based on the most common symptoms and the particular mutations that tend to cause them.


[edit] Types
In addition to the Mitochondrial myopathies, other examples include:

Diabetes mellitus and deafness (DAD)
this combination at an early age can be due to mitochondrial disease
Diabetes mellitus and deafness can be found together for other reasons as well
Leber's hereditary optic neuropathy (LHON)
visual loss beginning in young adulthood
Wolff-Parkinson-White syndrome
multiple sclerosis-type disease
Leigh syndrome, subacute sclerosing encephalopathy
after normal development the disease usually begins late in the first year of life, but the onset may occur in adulthood
a rapid decline in function occurs and is marked by seizures, altered states of consciousness, dementia, ventilatory failure
Neuropathy, ataxia, retinitis pigmentosa, and ptosis (NARP)
progressive symptoms as described in the acronym
dementia
Myoneurogenic gastrointestinal encephalopathy (MNGIE)
gastrointestinal pseudo-obstruction
neuropathy

[edit] Treatment
Although research is ongoing, treatment options are currently limited, though vitamins are frequently prescribed.[2]

Pyruvate has been proposed recently as a treatment option.[3]


[edit] References
^ Finsterer J (2007). "Hematological manifestations of primary mitochondrial disorders". Acta Haematol. 118 (2): 88�98. doi:10.1159/000105676. PMID 17637511.
^ "When Cells Stop Working" dated November 5, 2006 at Time Magazine
^ Tanaka M, Nishigaki Y, Fuku N, Ibi T, Sahashi K, Koga Y (2007). "Therapeutic potential of pyruvate therapy for mitochondrial diseases". doi:10.1016/j.mito.2007.07.002. PMID 17881297.

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"I wouldn't go out," Stacy Ritchey said. "And she said 'you and Dad said that when I got my cane and didn't want to go anywhere, that I had to face my friends because it was a part of me. I was afraid they'd stare and gawk. You still made me walk out that door.' She told me I was going to walk out that door. She's my hero."

Brittany has been diagnosed with Batten disease, a rare and progressive neurological degenerative genetic disease, and has been blind for six years. Her symptoms are progressing.

Stacy Ritchey, 32, and her daughters ― Savana is 6 ― live in a guest house above her parents' garage. The path to the door is a set of concrete steps. Brittany, whose legs muscles are splintering and deteriorating, already has fallen down them which is why they need of a chair lift, or an elevator.

"Her primary concern is helping her daughter, Brittany," said Paulette Craft, a clinical oncology social worker at Martin Memorial's cancer center. "She would love to have breast reconstruction ― this is near impossible to get a plastic surgeon to accept Medicaid for the procedure. But, her daughter is her main concern."

Stacy Ritchey was divorced from Brittany's father after marrying as a teen and has since been widowed twice. Savana's father, Tom Ritchey, died in 2005 in a collision when they lived in Pennsylvania.

Now, there is concern Savana is showing signs of the same disease that grips Brittany.

Brittany is undergoing more testing that won't be done until next summer and she might have mitochondrial disease, which mimics Batten's. If it is mitochondrial, Savana is almost certain to get it. If it's Batten's, Savana has a chance she might not get it.

Right now, that is a mother's best hope.

Wishbook wish: Chair lift ($15,000) or elevator ($60,000); new wheelchair ($2,800); help with gasoline bills for regular trips to Bascom Palmer Eye Clinic in Miami, Miami Children's Hospital and Dan Marino Hospital, no estimate; TV and Nintendo for youngest daughter; plastic surgeon willing to accept Medicaid for breast reconstruction.

How to donate: Paulette Craft, clinical oncology social worker