• Hyper – means more than normal (i.e. hyperactive means excessive activity)
  • Hypo – means less than normal (i.e. hypotonic means less than normal muscle tone)


  • -emia and -osis: Refers to blood (i.e. acidosis refers to acid in the blood, ketosis refers to ketones in the blood, hyperglycinemia refers to excess glycine in the blood.)
  • -uria: Refers to urine: (i.e. aminoaciduria means amino acids in the urine)



ACIDOSIS: Elevated amounts of organic acids in the blood, which accumulate when food is not properly metabolized.

ADP: Adenosine diphosphate; the low energy product produced when ATP releases energy to the cell.

ADVOCATE: One who supports or defends a cause. One who pleads on behalf of another.

ALPER DISEASE: Progressive Infantile Poliodystrophy. Cases of Alper disease may be caused by disorders of oxidative phosphorylation, including mitochondrial DNA depletion syndromes.

APHASIA: Impaired or absent language function, usually referring to speech; which results from an injury to brain structures usually in the dominant hemisphere (the side of the brain that controls language function is usually the side opposite to the handedness of the person and is referred to as the dominant hemisphere by definition).

ATAXIA: Un-coordination; Inability to coordinate the muscles in voluntary movement.

ATP: Adenosine triphosphate; cellular energy is stored in the third phosphate bond. ATP is formed from ADP and phosphate in the process known as oxidative phosphorylation.


BARTH SYNDROME: Cardiomyopathy-Neutropenia Syndrome. Marked by elevated levels of 3-methylglutaconic acid in the blood and urine.

BETA-OXIDATION: A series of metabolic reactions necessary for burning fatty acids (fats).


CARNITINE: (beta-hydroxy-gamma-N-trimiethylamino-butyrate). Responsible for the transport of long chain fatty acids into mitochondria.

CLONUS: An abnormal movement characterized by rapid contraction and relaxation of muscles.

CNS: Central nervous system (the brain and spinal cord).

COMPLEX I: NADH-Coenzyme Q oxidoreductase (part of the Electron Transport Chain).

COMPLEX II: Succinate dehydrogenase (part of the Electron Transport Chain).

COMPLEX III: Coenzyme Q-cytochrome c oxidoreductase (part of the Electron Transport Chain).

COMPLEX IV: Cytochrome c oxidase (COX) (part of the Electron Transport Chain).

COMPLEX V: ATP synthase (part of the Electron Transport Chain).

COX: Cytochrome c oxidase (Complex IV).

CPEO: Chronic Progressive External Ophthalmoplegia Syndrome. The combination of ptosis and restricted eye movements is referred to as opthalmoplegia.

CYTOCHROME: A type of protein whose function is to carry electrons or protons (hydrogen ions) by virtue of the reversible charging/discharging of an iron atom or iron/sulfur atoms in the center of the protein. Cytrochromes are central molecules of electron transport in the process known as oxidative phosphorylation. The “chrome” means color, and these cytochromes are divided into four groups. (a, b, c, d) according to their ability to absorb or transmit certain colors of light.

CYTOPATHIES: A pathologic process or disease of the cell or components of the cell.


DYSPHASIA: Lack of coordination in speech, and failure to arrange words in an understandable way; due to brain lesion. Aphasia is the complete or near complete absence of speech, and is used to describe a more severe situation than dysphasia.

DEMENTIA: loss of cognition and mental functions due to a disease or disease process.

DNA: Deoxyribonucleic acid; a two-stranded molecule that contain the genes that provide the blueprint for all of the structures and functions of a living being. Most human DNA is nDNA, which is a huge molecule that is folded tightly and stored in the nucleus of the cell. MtDNA is a much smaller molecule stored in the mitochondria.

mtDNA: Mitochondrial DNA contain the genes that code for some of the enzymes and some of the necessary molecules needed to make those enzymes of the respiratory chain. Mitochondria are the only part of the body cell with their own separate and unique DNA. Regardless, most of the mitochondria and the respiratory chain are coded by nDNA. MtDNA is inherited only from the mother.

nDNA: Nuclear DNA; located in the nucleus of the cell, this DNA contains the blueprints for cells which make up the body.


ELECTRON TRANSPORT CHAIN (ETC.): Also known as the respiratory chain: The mitochondrial enzymes (also known as complexes I, II, III and IV) that are needed to generate the electron and proton “gradient” that is utilized by complex V to generate ATP.

ENCEPHALOPATHY: Any disease of the brain.

ENZYME: A protein that speeds up a chemical reaction or causes a chemical change in another substance. Enzymes do their work without being changed or used up in the process.


GENE: The fundamental unit of heredity. Genes are located on strands of DNA found in the cells and mitochondria.



HEMIANOPSIA: Loss of vision, due to brain malfunction, for the right or left portion of vision, which may involve either or both eyes.

HYPOTONIA: Poor muscle tone, such as seen in “floppy babies”.


KSS: Kearns-Sayre Syndrome, which is the combination of CPEO, cardiac conduction defects and progressive hearing loss, usually due too a large deletion in part of the mitochondrial DNA.


LACTATE or LACTIC ACID: A chemical that is formed when sugars are broken down for energy without the presence of adequate oxygen. Lactic acid cannot be used by the body and will accumulate in blood and urine. Lactic acid causes the muscle pain when one runs too fast for too long. In people with mitochondrial disorders, lactic acid forms when the oxidative capacity (ability to burn foods using oxidative phosphorylation) of the person is impaired.

LCFA: long chain fatty acids, which make up the vast majority of fats we consume in our diet.

LCAD: Long-Chain Acyl-CoA Dehydrongenase Deficiency.

LEIGH DISEASE OR SYNDROME: Subacute Necrotizing Encephalomyelopathy.

LHON: Leber Hereditary Optic Neuropathy.

LIC: Lethal Infantile Cardiomyopathy.


MAD: Multiple Acyl-CoA Dehydrogenase Deficiency.

MCAD: Medium-Chain Acyl-CoA Dehydrongenase Deficiency.

MELAS: Mitochondrial Encephalomyopathy Lactic Acidosis and Strokelike Episodes.

MERRF: Myoclonic Epilepsy and Ragged-Red Fiber Disease.

METABOLISM: The process of cells burning food to produce energy. This is similar to a car’s engine (the cell’s mitochondria) burning gasoline (the food we eat) to produce the energy or torque that turns the drive train that spins the car’s wheels (the energy we need to move and think).

MITOCHONDRIA: A part of the cell (organelle) that is responsible for energy production. The organelle consists of two sets of membranes, a smooth continuous outer coat and an inner membrane arranged in tubules or in folds that form plate-like double membranes (cristae); the principal energy source of the cell, containing the cytochrome enzymes of terminal electron transport and the enzymes of the citric acid cycle, fatty acid oxidation, and oxidative phosphorylation. Responsible for converting nutrients into energy as well as many other specialized tasks.

MITOCHONDRIAL CYTOPATHY: Disease process characterized by mitochondrial dysfunction. The preferred general term for referring to mitochondrial diseases.

MITOCHONDRIAL ENCEPHALOPATHY: Disease process characterized by mitochondrial dysfunction in the brain.

MNGIE: Myoneurogastointestinal Disorder and Encephalopathy.

MYOCLONUS: A single spasm or twitching of a muscle. Myoclonus can be a single event (twitch) or repeated events. Myoclonus can be a normal event (the jerks that occur when we fall asleep) or an abnormal event (those that occur while awake, or those associated with seizures or mitochondrial diseases). Clonus is the repeated spasms of muscles, due to a seizure or increased muscle tone.

MYOPATHY: Any abnormal conditions or disease of the muscle tissues, which include the muscles over our bones (skeletal muscle) and the heart (cardiac muscle).


NARP: Neuropathy Ataxia and Retinitis Pigmentosa.

NYSTAGMUS: Involuntary, erratic eye movements.


PARENTAL EMPOWERMENT: Parents taking charge, assuming responsibility and exercising appropriate and rationale power in a situation. (i.e.: obtaining a second opinion, requesting copies of laboratory reports, requesting or rejecting a muscle biopsy).

PEARSON SYNDROME: A severe disease occuring in infancy affecting bone marrow and pancreas function. Infants with Pearson syndrome may develop KSS as they get older.

PHD: Pyruvate Dehydrogenase Deficiency.

PHOSPHORYLATION: The addition of phosphate to an organic compound, such as the addition of phosphate to ADP to form ATP (the function of complex V in the electron transport chain) or the addition of phosphate to glucose to produce glucose monophosphate, through the action of enzymes known as phosphotransferases or kinases.

POINT DELETION: The deletion of a single nucleotide amino acid on a gene.

POINT MUTATION: The substitution of one nucleotide for another nucleotide amino acid on a gene.

PTOSIS: Droopy eyelids.


RESPIRATORY CHAIN: See Electron Transport Chain.


SCAD: Short-Chain Acyl-CoA Dehydrogenase Deficiency.

SEIZURES : Disturbances of brain function, manifested as episodic impairment or loss of consciousness, abnormal movement, or sensory disturbances. Caused by paroxysmal disturbances in the electrical activity of the brain.

  • Myoclonic: Seizures characterized by jerking a body extremity or generalized tonic-clonic seizures within an hour or two of waking from sleep.
  • Partial: (Formerly known as focal seizures.) The seizure is limited to one area in the brain. During this type of seizure, the child may experience a range of strange or unusual sensations including sudden, jerky movements of one body part, distortions in hearing or seeing, stomach discomfort, or a sudden sense of fear. Partial seizures are classified as either simple or complex. In simple partial seizures, there is no loss of consciousness. In partial complex seizures, consciousness is impaired.
  • Petit-mal: Now called generalized absence seizures. These are characterized by 5 to 15 second lapses in consciousness. During an absence seizure, the child appears to be staring into space and the eyes may roll upwards. Absence seizures typically occur in childhood and resolve in adolescence. Absence seizures are rare in adults.

SNE: Subacute Necrotizing Encephalomyelopathy, or Leigh Disease or Syndrome.

SYNDROME: The aggregate of and symptoms associated with any morbid process and constituting together the picture of the disease. Syndromes can be, but are not necessarily the same as the disease. For example, titubation is a syndrome and never referred to as the disease, while myopathy can be used properly to describe a syndrome or a disease (although most prefer to further subclassify a myopathy in order to be more specific).


TITUBATION: The appearance of staggering or stumble.