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Leukodystrophy glossary

There are many confusing medical terms related to leukodystrophy.

That’s why we’ve created this glossary. We hope it helps you navigate what can be a difficult experience.

  • Produced by the pituitary gland, its key function is to stimulate the production and release of cortisol from the cortex of the adrenal gland
  • Also called primary adrenal insufficiency, this occurs when adrenal gland production of cortisol is chronically deficient, resulting in elevated ACTH levels. Primary adrenal insufficiency is found in 85% of young boys who develop the most severe form of ALD.
  • These sit on top of each kidney and produce (secrete) three types of hormones: Glucocorticoid hormones produce cortisol which help maintain sugar (glucose) control, decrease immune response and helps the body to respond to stress Mineralocorticoid hormones produce aldosterone which(...)
  • ALD Life is the former name of Alex TLC.
  • The variant form of a gene. For example, the gene for eye colour has several variations (alleles) such as an allele for blue eye colour or an allele for brown eyes.
  • Transplanted cells are coming from a donor – this may be a sibling, other relative, or someone unrelated to the patient (the cells can even come from umbilical cord blood)
  • A general term for hair loss or sparse hair
  • Partial or total vision loss without visible changes to the eye
  • Shortage of red blood cells, causing fatigue, weakness and lack of energy as insufficient amounts of oxygen are transported around the body. Iron deficiency anaemia is a common type of anaemia caused by a lack of iron in the blood
  • Small dark red spots caused by enlarged blood vessels. These benign spots or lesions are more common in older people
  • Temporary interruptions to breathing, especially during sleep – this is also known as Sleep Apnoea or Obstructive Sleep Apnoea (OSA). Over time, those with apnoea can feel increasingly fatigued, as breathing may be interrupted hundreds of times a night. There are a range of treatments(...)
  • Lack of muscle coordination which may affect speech, eye movements, the ability to swallow, walking, picking up objects and other voluntary movements. A person with persistent ataxia may have damage in the part of the brain that controls muscle coordination – the cerebellum
  • Abnormal muscle contraction causing slow, involuntary writhing of the limbs, possibly continuously
  • Wasting away or decrease in size of an organ or tissue in the body. When a body part is affected by an inability to function, the muscles may atrophy through lack of use and especially as a result of the degeneration of cells
  • Transplanted structures or cells came from you and your body. In an autologous transplant the patient “donates” their cells to theirself
  • Damage to the nerves of the autonomic nervous system, causing dizziness, problems with digestion, urination, vision and sexual problems
  • Expressed in individuals who have just one copy of the mutant allele. Affected individuals have one normal copy of the gene and one mutant copy of the gene, thus each offspring has a 50% chance of inheriting the mutant allele. Approximately half of the children of affected parents inherit the(...)
  • Gene responsible for the phenotype is located on one of the 22 pairs of autosomes (non-sex determining chromosomes).
  • Clinically manifest only when an individual has two copies of the mutant allele. When just one copy of the mutant allele is present, an individual is a carrier of the mutation, but does not develop the condition. Females and males are affected equally by traits transmitted by autosomal(...)
  • Any of the numbered chromosomes, as opposed to the sex chromosomes. Humans have 22 pairs of autosomes and one pair of sex chromosomes (the X and Y). Autosomes are numbered roughly in relation to their sizes: chromosome 1 has approximately 2,800 genes, while chromosome 22 has approximately 750(...)
  • A Bone Marrow Transplant (BMT) replaces bone marrow stem cells in people whose bone marrow has been destroyed by large doses of chemotherapy or radiotherapy. This prepares your body for the donor bone marrow. The healthy stem cells are put into your body intravenously (IV), then find their(...)
  • Unusually slow or difficult body movements, making everyday movements take much longer. Parkinson’s Disease is the most common, but not the only possible, cause
  • Symptoms which relate to the function of cranial nerves, including dysphagia, dysphonia and dysarthria
  • Unusual, permanent curvature of one or more of the fingers, always including the little finger
  • Abnormally enlarged heart. This can be temporary or permanent, and can either cause no symptoms or cause shortness of breath, swelling and an irregular heart beat (arrythmia)
  • The central nervous system (CNS) consists of the brain and the spinal cord. The spinal cord carries out automatic motor responses, transmits sensory information to the brain and transmits messages from the brain to the muscles and organs. Each of the spinal cord's segments controls sensation(...)
  • Relates to the cerebellum, the large structure at the back of the brain that receives information from the sensory systems, the spinal cord, and other parts of the brain and then regulates motor movements. The cerebellum coordinates voluntary movements such as posture, balance, coordination,(...)
  • Reduction or stoppage of bile flow between the liver and small intestine, causing some waste products to accumulate in the bloodstream rather than being expelled in stools or urine. This can cause yellow (jaundiced) skin, light-coloured stools, dark urine and itchiness and can be caused by(...)
  • A sample is taken from the lining of the uterus (Chorion) which becomes the placenta 11-13 weeks from gestation. This contains foetal tissue and the DNA which is tested for the known mutation, VLCFA’S and other tests that look at chromosome make up, size etc (Karyotyping) to diagnose(...)
  • A long strand of DNA that contains many genes; there are 46 human chromosomes (22 pairs of chromosomes, and the X and Y chromosomes). Women have 44 autosomes plus two copies of the X chromosome. Men have 44 autosomes plus an X and a Y chromosome.
  • An opening in the roof of the mouth (palate) or upper lip, present from birth. This is the most common facial birth defect in the UK and is treatable with surgery. Without or before surgery, this can affect ability to hear and speak as well as creating dental and feeding issues
  • Impaired ability of the blood to form clots (coagulate). This may mean that prolonged or excessive bleeding occurs, either spontaneously or after injury
  • The destruction, removal or loss of the myelin sheath on a nerve or nerves. The myelin sheath is the protective covering around the nerve; damage to this causes nerve impulses to slow or stop, meaning messages sent by the brain cannot be received elsewhere in the body
  • Deoxyribonucleic acid (DNA) is contained in your body's cells. It is a double, long chain of molecules called nucleotides that tell each cell what proteins to make. The DNA itself makes up chromosomes
  • Speaking difficulties caused by brain damage. Those with dysarthria may have slurred, nasal-sounding or breathy speech
  • A type of ataxia, dysmetria is a lack of coordination of movement. This can be linked to an inability to judge scale or distance
  • Defective or malformed myelin sheath - as opposed to demyelination, where the previously normal myelin sheath is damaged or destroyed
  • Swallowing difficulties ranging from problems with certain foods to a complete inability to swallow
  • Speaking difficulties caused by physical disorder of the mouth or throat
  • Abnormal muscle tone resulting in muscular spasm and abnormal posture, typically due to neurological disease. Dystonia is characterised by involuntary muscle contractions that cause slow repetitive movements or abnormal postures. The movements may be painful, and some individuals with(...)
  • A general term for brain disease, damage or malfunction, causing an altered mental state
  • A collection of glands that secrete chemicals directly into the bloodstream. These chemicals are called hormones and some of those are: cortisol, aldosterone, adrenaline, noraadrenaline, testosterone, oestrogen, oxytocin and dopamine. The main endocrine glands include pituitary, pineal and(...)
  • An enzyme is made from a group of complex proteins that are produced by living cells and act as catalysts in specific biochemical reactions. They speed up the chemical process. Not all enzymes are made from Amino therefore are not proteins. Enzymes are named by what they do
  • The study of patterns, causes, and effects of health and disease conditions in defined population
  • Limited ankle motion, inability to flex the foot towards the front of the leg
  • Red skin caused by increased blood flow after injury, infection or inflammation
  • Spaces between the bones of the skull as an infant develops, colloquially known as ‘soft spots’
  • Gadolinium is used as a contrast agent to improve the visibility of internal body structures in magnetic resonance imaging (MRI). When having an MRI for ALD, gadolinium enhancement can show areas of inflammation/active disease within the brain
  • Sometimes referred to as a PEG (percutaneous endoscopic gastrostomy), this is a procedure in which a flexible feeding tube is placed through the abdominal wall and into the stomach. PEG allows nutrition, fluids and/or medications to be put directly into the stomach, bypassing the mouth and throat
  • Designed to introduce genetic material into cells to compensate for abnormal genes or to make a beneficial protein. It involves removing a sample of the patient’s bone marrow – the building block of all of the body’s immune cells – and exposing them to viruses carefully modified to carry a(...)
  • The genetic material of an organism
  • An individual’s collection of genes. The term also can refer to the two alleles inherited for a particular gene. The genotype is expressed when the information encoded in the gene’s DNA is used to make protein and RNA molecules. The expression of the genotype contributes to the individual’s(...)
  • A supportive cell in the central nervous system. Unlike neurons, glial cells do not conduct electrical impulses. The glial cells surround neurons and provide support for and insulation between them. Glial cells are the most abundant cell types in the central nervous system. Types of glial(...)
  • Large cells which usually have more than one nucleus
  • GVHD may occur after a bone marrow or stem cell transplant in which someone receives bone marrow tissue or cells from a donor. This type of transplant is called allogenic. The newly transplanted cells regard the recipient’s body as foreign. When this happens, the newly transplanted cells(...)
  • The “grey matter” of the brain gets its colour from the cell bodies, dendrites and the unmyelinated axons
  • An immature cell that can develop into all types of blood cells, including white blood cells, red blood cells, and platelets. Hematopoietic stem cells are found in the peripheral blood and in the bone marrow. They are used in Bone Marrow Transplants (BMT) because the transplant of healthy(...)
  • Abnormally enlarged liver
  • Abnormally enlarged liver and spleen
  • An individual who has two different forms of a particular gene (allele), one inherited from each parent
  • An individual who inherits the identical forms of a particular gene (allele) from each parent
  • Accumulation of cerebrospinal fluid in the brain, increasing pressure
  • The extension of the limbs beyond their normal movement
  • Overactive or over-responsive reflexes, including twitching and spasticity
  • An abnormally increased distance between two body parts, most commonly the eyes
  • Thickening of heart muscle forcing the heart to work harder
  • Developmental absence of one or more teeth, affecting both childhood and permanent teeth
  • Low blood sugar
  • Decreased response of the deep tendon reflexes, usually resulting from injury to the central nervous system or a metabolic disease
  • Sudden fall in blood pressure when standing up
  • An abnormality of the skeletal muscle tone, which is indicative of genetic disorders or nervous system dysfunction. Patients with these tendencies display floppy limbs and an inability to sustain normal head position
  • Persistent dry, scaly skin covering large areas of the body
  • Calculated as the number of new cases of a disease or disorder in a specified time. It is calculated by the number of new cases of a disease or disorder in a specified time, usually a year, divided by the population that is being considered. In rare diseases it can be very small and is often(...)
  • IWMD stands for Inherited White Matter Disorders, and is another term for leukodystrophy. You may hear the conditions referred to with either of these terms. Leukodystrophies may be referred to as Inherited (or genetic) White Matter Disorders (IWMDs) meaning that the affected person(...)
  • Abnormal spine curvature in two places, combining outward curvature (kyphosis) and lateral curvature (scoliosis) of the spine
  • This simply means abnormal white matter in the brain and does not imply a genetic cause
  • Developed to measure the loss of myelin shown on a brain MRI.  The higher the points the more myelin loss and it has a direct correlation to functionality.
  • Unusually large head
  • This procedure uses a very powerful magnetic field and radio waves to contrast the various soft tissues that we have in our bodies. This makes it ideal for looking at our brain. From the results the radiologists can see the difference in the white matter in our brain and where it is deficient(...)
  • Unusually large brain
  • Unusually small head
  • The primary immune cells of the CNS. They act as the major inflammatory cell type in the brain and respond to pathogens (disease carriers) and injury by becoming “activated” – a process whereby they rapidly change form, proliferate and migrate to the site of infection/injury where they eat(...)
  • Undersized jawbone, also known as mandibular hypoplasia
  • Developmental disorder of the eye, causing one or both eyes to be abnormally small
  • The power houses of the cell providing the body with over 90% of the energy it needs to sustain life.  Mitochondrial disease is a debilitating and potentially fatal disease that reduces the ability of the mitochondria to produce this energy
  • The insulation material that is made from proteins and lipids (fats etc) that is produced in the neuron to coat and protect the transmission arm of the neuron – the axon. This process is called Myelination.  Myelin is a spongy substance which is white in appearance and is referred to as “the(...)
  • Muscle weakness due to improper functioning of muscle fibres
  • This term includes CAT Scans (Computerised Axial Tomography) and MRI’s (Magnetic Resonance Imaging)
  • A neuron is a nerve cell. There are three types of neurons: sensory, motor and interneurons
  • Constant uncontrolled eye movements
  • Weakness of muscles which move the eyes
  • Abnormality in the optic nerve, which carries information from the eye to the brain
  • Low bone density making bones weaker than normal
  • Thinning bones, causing a tendency for fractures
  • Abnormal development of the ovaries (the term gonadal dysgenesis refers to abnormal development of reproductive systems in both men and women)
  • Spasms in the roof of the mouth (palatal muscles)
  • Paraparesis (paraplegia) refers to partial (-paresis) or complete (-plegia) loss of voluntary motor function in the lower limbs (legs and feet).
  • A pricking sensation, numbness or weakness in hands and feet
  • Episodic abnormal movements affecting one or both sides of the body, ranging from mild to severe. These jerking or shaking movements are induced by sudden motion, such as being startled or standing up quickly
  • Consists of neurons that carry messages to and from the central nervous system. The PNS sends information to and from the body’s internal structure that carry out basic life processes such as digestion and breathing
  • A condition that develops as a result of damage to the peripheral nervous system — the vast communications network that transmits information between the central nervous system (the brain and spinal cord) and every other part of the body. Symptoms can range from numbness or tingling, to(...)
  • A specialist part of a cell containing proteins and performing essential metabolic functions, such as the decomposition of fatty acids
  • An individual’s traits you can see such as height, eye colour, and blood type or the presence/absence of a disease. An individual's phenotype is largely determined by their genotype (genetic makeup), while other traits are largely determined by environmental factors like diet, exercise,(...)
  • Increased sensitivity to light
  • One or more extra toes or fingers, on one or both feet or hands
  • High blood pressure to the liver
  • The number of living cases of a disease or disorder that exist at any point in time. In rare diseases it can be shown as the number of people per 100,000
  • Protruding upper or lower jawbone
  • Required for the structure, function, and regulation of the body's cells, tissues, and organs
  • Paralysis caused by illness or injury to a human that results in the partial or total loss of use of all their limbs and torso; Paraplegia is similar but does not affect the arms. The loss is usually sensory and motor, which means both sensation and control are lost
  • Sideways curvature of the spine. Most cases of scoliosis are mild, but some children develop spine deformities that continue to get more severe as they grow. Severe scoliosis can be disabling. An especially severe spinal curve can reduce the amount of space within the chest, making it(...)
  • A state of increased tone of a muscle (and an increase in the deep tendon reflexes). For example, with spasticity of the legs (spastic paraplegia) there is an increase in tone of the leg muscles, so they feel tight and rigid and the knee jerk reflex is exaggerated
  • abnormally enlarged spleen 
  • Degeneration of the discs of the spine
  • The medical term for a squint, a condition where the eyes point in different directions. One eye may turn inwards, outwards, upwards or downwards while the other eye looks forward
  • Some or all fingers or toes are wholly or partially united, creating webbed skin. Underlying bones may or may not be fused together
  • Hearing noises not caused by an outside source, such as a ringing in the ears, either continuously or sporadically
  • Restricted up-and-down eye movement, also known as Parinaud’s Syndrome
  • Abnormally large abdominal organs
  • Neural tissue in the brain and spinal cord consisting of myelinated axons (nerve fibres). The white matter of the brain allows communication between different regions of the brain and between the brain and spinal cord. As the name suggests, white matter is white in colour due to the myelin.
  • A mode of genetic inheritance where the gene responsible for the disorder is located on the X chromosome. This typically means that the disease or disorder will have a greater effect on males: Males have one X and Y chromosome, females have two X chromosomes. This means that if a female has a(...)
  • Yellowish, cholesterol-rich deposits seen anywhere on the body, showing abnormal storage of fats