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Glossary of medical terms

You may come across some of the following terms being used in relation to your GSD.

We have tried to provide a layman’s explanation of each term. Where there is a difference in meaning or application between the various GSDs, we have highlighted this.

For more technical medical definitions try this medical dictionary.
Go to online medical dictionary.

Please note: on some devices, you may need to click a second time on your chosen letter of the alphabet.

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  • Acid Maltase DeficiencyAnother name for Pompe disease. Acid Maltase is a term for the GAA enzyme. People with Pompe disease lack or produce very low levels of this enzyme, they have a deficiency. This term was more common historically and in the USA.
  • AcuteSudden and severe.
  • Acute renal failureARF, a sudden decline in kidney function. Requires urgent medical attention. Muscle GSDs: ARF can be caused by the breakdown of muscle from anaerobic activity.
  • Adenosine triphosphateATP, a molecule in muscle cells which serves as an energy source for the metabolic process.
  • Aerobic exerciseExercise which requires oxygen to assist in converting fuel sources into energy. Walking is a good example of aerobic exercise. This is good exercise for those with McArdle disease.
  • Alanine aminotransferaseALT, an enzyme produced mainly in the liver. Also known as alanine transaminase.
  • AlbuminA protein made by the liver. Controls fluid in the blood and tissues.
  • Alkaline phosphataseALP/ALK-PHOS, an enzyme produced in the bile ducts and elsewhere in the body.
  • ALTAlanine transaminase (also know as alanine aminotransferase) an enzyme found mostly in the liver. Levels are sometimes higher in people with Pompe disease.
  • AnaemiaA lack of iron can lead to a person having fewer red blood cells than usual. There can also be other causes.
  • AnaerobicWithout oxygen. A type of activity which uses stored energy rather than blood-borne energy.
  • Anaerobic exerciseExercise which does not need oxygen to utilise fuel sources. Weightlifting is a good example of anaerobic exercise. This type of exercise requires the conversion of glycogen to glucose.
  • AnastomosisA connection made surgically between two tubes.
  • AngiogramA scan using x-rays to see blood vessels. It can be used to see the blood vessels which supply the liver.
  • ArrythmiaIrregular rhythm often describing the way the heart beats. This includes; too fast, too slow or fluttering.
  • AscitesFluid collecting in the abdomen.
  • Aspartate aminotransferaseAn enzyme produced mainly in the liver.
  • AtelectasisCollapse or closure of a lung.
  • AtresiaBlocked, destroyed or missing.
  • AtrophyWasting away or degeneration.
  • Autosomal recessiveOne pattern in which a child inherits genes from parents. The disease only occurs when a child inherits two copies of a defective gene (one from each parent).
  • BandingTreatment for varices. Surgical elastic bands are placed around the varices during an endoscopy.
  • BileGreen/yellow liquid containing bile salts, bilirubin and cholesterol.
  • Bile acidsAcids found in bile which can be converted into bile salts.
  • Biliary tractThe system of tubes which carry bile from the liver and gall bladder and drain into the intestine.
  • BilirubinProduct of the breakdown of old red blood cells. It has a yellow colour which gives stool and blood their colour. Bilirubin travels in the blood stream to the liver where it has a sugar added and becomes conjugated bilirubin.
  • BiopsyProcedure to take a small sample of tissue to test in the laboratory. In GSDs these are usually from the liver or muscle.
  • BiPaPType of non-invasive ventilator that helps with breathing. This type is Bi-Level Positive Airway Pressure which delivers variable respiratory and lower expiratory pressure for easier breathing.
  • Blood GlucoseAmount of glucose that is in your blood.
  • Body Mass IndexBMI, a test using height and weight to measure whether an individual is a healthy weight.
  • CannulaA short, soft, narrow plastic tube temporarily put into a vein so medicines/fluids/blood etc. can be given intravenously (IV) as needed.
  • CarbohydrateA type of compound, such as starches and sugars, found in food. Broken down in the body to form energy.
  • CardiacOf the heart.
  • CardiomegalyAbnormal enlargement of the heart.
  • CardiomyopathyDisease of the heart muscle, where the walls of the heart chambers have become stretched, thickened or stiff. This affects the heart's ability to pump blood around the body.
  • Cardiovascular systemThe heart and blood vessels which transport nutrients and oxygen around the body.
  • CellBasic structural and functional component of all living things.
  • Central venous lineCVL, a central line is similar to a cannula but is a longer tube used to give medicine, fluid, nutrition or blood directly into a larger vein. Can also be used to take blood samples. Long, narrow plastic tube placed into a vein in the neck, chest or groin, used for longer than a cannula.(...)
  • CholangitisInflammation or infection of bile ducts which can cause poor bile flow from the liver and liver damage.
  • CholestasisReduction or blockage of bile flow.
  • ChronicAn illness or condition which lasts over a period of time.
  • Chronic HepatitisInflammation of the liver that lasts over a period of time. Liver cells may be destroyed by the inflammation.
  • CoagulopathyAny condition where the blood cannot clot properly.
  • Computerised tomography scanCT Scan, x-rays are used to create a detailed picture of parts of the body.
  • CongenitalCondition which is present from birth.
  • CPAPA type of non-invasive ventilator that helps with breathing. This type is Continuous Positive Airway Pressure which applies mild air pressure on a continuous basis to keep the airways continuously open.
  • Creatine kinaseAbbreviated to CK or CPK. An enzyme which is used in the formation of ATP in muscle. People muscle GSD have a raised level of CK in their blood and this is often an early sign that something is wrong.
  • CRIMCross Reacting Immune Material. If the body is producing a low level of GAA enzyme when the enzyme treatment [ERT] is given as a treatment the body recognizes it. However, if the body has zero GAA [CRIM Negative] when the enzyme treatment is given the body treats it as a foreign object and the(...)
  • CysticRelating to the gall bladder
  • CytomegalovirusCMV, a virus belonging to the herpes virus group.
  • DieticianA degree-qualified health professional who helps to promote nutritional well-being, treat disease and prevent nutrition related problems. They provide practical, safe advice, based on current scientific evidence.
  • DistensionExpansion or enlargement.
  • DuctTube which fluid can pass through from one part of the body to another, e.g. bile ducts.
  • DWPThe Department for Work and Pensions is responsible for welfare, pensions and child maintenance policy. As the UK's biggest public service department it administers the State Pension and a range of working age, disability and ill health benefits.
  • Dysplasia.Abnormal development of body tissue or an organ
  • ECGElectrocardiogram. A recording of the beating of the heart made by placing sensors on your chest and limbs. It is printed out as a trace or graph.
  • EchocardiogramEcho, a scan of the heart using high frequency sound waves, similar to an ultrasound of the abdomen.
  • ElectrocardiogramThe measurement of electrical activity in the heart and its recording as a visual trace, using electrodes placed on the skin of the limbs and chest.
  • EncephalopathyChanges in the brain which can be due to liver failure. The build-up of toxins in the blood can lead to tiredness, irritability and personality changes.
  • EndoscopyUsing a flexible, thin tube with a camera attached to look at the inside of the upper end of the digestive system. It is passed through the mouth and down the oesophagus (the food tube).
  • Enteral feedingFeeding through a tube directly into the stomach or part of the intestine.
  • EnzymeA protein which the body uses to make a chemical reaction happen.
  • Epstein Barr virusEBV, a virus which causes glandular fever.
  • ERCPEndoscopic retrograde cholangiopancreatography, a special x-ray used to examine bile ducts under general anaesthetic.
  • ERTEnzyme Replacement Therapy.
  • ESAEmployment and Support Allowance is for people of working age who cannot work because of illness or disability. Entitlement usually depends upon your National Insurance record (except for some young adults), and may be subject to a medical assessment.
  • FaecesAlso known as stool or poo.
  • FibrosisScar tissue which replaces normal tissue which, when extensive, is known as cirrhosis.
  • Forbes DiseaseAnother name for GSD3 in honour of American clinician Gilbert Burnett Forbes.
  • Full blood countFBC, blood test measuring all of the different types of cells in the blood.
  • FulminantSevere, sudden form of liver failure. More commonly known as acute liver failure.
  • GAALysosomal acid alpha-glucosidase. One of the enzymes needed in the metabolism of glycogen but missing or in very low levels in people with Pompe disease.
  • GallbladderSmall sac which stores and releases bile made by the liver.
  • GallstonesStones which can be formed by bile and collect in the gall bladder and bile ducts. They can cause pain and may pass into the common bile duct and cause cholangitis or obstructive jaundice.
  • GastroenterologyStudy of the digestive system.
  • General anaestheticAn individual is put into a state of controlled unconsciousness.
  • GenesMade up of DNA and provide instructions for the body.
  • GenomeAll the genes together are called the genome. Each living thing has its own genome, the entire collection of genes.
  • GlucoseThe end product of carbohydrate metabolism and also found in certain foods such as fruit. The chief source of energy.
  • GlycogenThe form in which glucose is stored in the muscles and in the liver. It has to be converted back to glucose to be used for energy.
  • GlycolysisThe conversion of glycogen and glucose, via a series of steps, finally into ATP which energises the muscle. The process does not use oxygen and is thus anaerobic.
  • GraftOrgan, tissue or cells used for transplantation.
  • HaematemesisVomiting blood.
  • HaemoglobinPart of a red blood cell which carries oxygen around the body.
  • HepaticOf the liver.
  • Hepatic arteryBlood vessel which brings blood with oxygen to the liver.
  • Hepatic veinBlood vessel which takes blood away from the liver.
  • HepatitisInflammation of the liver.
  • HepatologyStudy of the liver.
  • HepatomegalyEnlargement of the liver.
  • HydrotherapyUsing water as a treatment or therapy. This can be either cold, warm or hot water and often means exercises or movements in the water.
  • HypertensionHigh blood pressure.
  • HypoglycaemiaDeficiency of glucose in the bloodstream. Often called low blood sugar. May be associated with symptoms such as anxiety, sweating, tremor, palpitations, nausea, and pallor.
  • HypotensionLow blood pressure.
  • HypotoniaPoor or low muscle tone, often seen as floppy, weak muscles.
  • IdiopathicSomething with no known cause.
  • ImmunityProtection against a particular disease, occurring naturally or due to vaccination.
  • ImmunoglobulinProtein which plays a role in the immune system.
  • ImmunosuppressionMedications which make the immune system less active.
  • IncidenceNumber of new cases of a disease over a certain period of time in a population.
  • International normalised ratioINR, a measure of how well blood clots.
  • IntravenousInto the vein. Some fluids and drugs are delivered into the veins.
  • IsometricMuscular action in which tension is developed without contraction of the muscle. Also known as 'static' exercise as there is no movement of the muscle. For example: clenching fists, holding something up or pushing.
  • JaundiceHigh level of bilirubin in the blood leading to yellowing of the skin and/or the whites of the eyes.
  • Kasai portoenterostomyOperation to get bile flowing from the liver to the intestine in biliary atresia. Bile ducts are removed and a piece of intestine is used to replace the ducts.
  • Lactic acidAn acid which is made as a biproduct of the muscle using carbohydrate. Normally there is a rise of lactic acid in the bloodstream on exercise.McArdle disease - it does not rise. The lack of this rise can be a help in diagnosis.
  • Liver function testsLFT, blood tests which can show how well the liver is working.
  • LymphClear, watery liquid derived from body tissues which carries white blood cells and fats. It travels through the lymphatic system of the body.
  • LymphadenectomyOperation to remove the lymph nodes.
  • LysosomeFound inside a cell, they digest or recycle waste from cell metabolism.
  • Malignant hyperthermiaA severe form of fever caused by a reaction to certain anaesthetics and muscle relaxants. Those with muscle GSD disease may be at an increased risk of malignant hyperthermia and should always tell their anaesthetist about their condition before having a general anaesthetic.
  • Metabolic disorderA condition in which metabolism is affected.
  • MetabolismProcesses in the body which break down and build up different chemicals in the use of energy. The process simply starts with taking in food.
  • MitochondriaA very small organ within the cells of the muscle which is responsible for energy production from fuels. Through regular aerobic exercise the number of mitochondria can be increased, which boosts the aerobic capacity of the muscle.
  • Muscle BiopsyA medical procedure in which a small piece of muscle is removed from the body and tested.
  • MutationA permanent change or alteration. Can occur within the gene.
  • MyalgiaPain in a muscle or muscles. This the main symptom of muscle GSDs.
  • MyoglobinA protein found in red skeletal muscle.
  • MyoglobinuriaPresence of myoglobin in the urine. Muscle damage releases myoglobin into the blood and the kidneys remove it from the blood to the urine. An excessive amount of myoglobin in the blood can "block" the kidneys and cause acute renal failure.
  • MyopathyA disease of the muscle.
  • MyophosphorylaseThe muscle type of phosphorylase. Deficient in McArdle disease. There are also brain and neo-natal forms.
  • NasogastricNG feeding, giving food through a tube which goes through the nose and down the throat to the stomach.
  • Nasogastric tubeTube used during nasogastric feeding.
  • Nasojejunal tubeNJ, small tube that is passed up the nose and down the throat, through the stomach, and into the small intestine used for feeding.
  • Natural HistoryThe course of the disease and how it progresses when no treatment is given. Treatments can change the course of the disease and alter the way it progresses from the natural history.
  • NeuromuscularOf the muscle and nerves. People with muscle glycogen storage disease may be diagnosed and/or cared for by a neuromuscular consultant.
  • NIVNon Invasive Ventilation when air is supplied via a mask over the nose and/or mouth.
  • Occupational Health TherapistProvides practical support to help children and adults of all ages, with mental, physical, social or learning disabilities, to independently carry out everyday tasks or occupations with more confidence and independence.
  • OedemaA build up of fluid in the affected tissues. Also known as fluid retention.
  • OsteopeniaBones that are weaker than normal.
  • Parenteral nutritionPN, feeding nutrients directly into the vein when an individual cannot eat normally.
  • Percutaneous Transhepatic CholangiographyPTC, special x-ray which looks at the bile ducts. Done under a general anaesthetic using a needle which is inserted through the skin of the abdomen into the bile ducts.
  • PhlebotomistPerson who takes blood samples.
  • PhosphorylaseAn enzyme used in the conversion of stored glycogen to glucose so that it can be utilised for energy.
  • PhysiotherapyA therapy to help restore movement and function when someone is effected by injury, illness or disability. A neuromuscular physiotherapist would be needed to teat a person with a glycogen storage disease affecting muscle.
  • PlateletsPart of the blood, important for clotting the blood. Can be low in people with liver disease.
  • Polymerase Chain ReactionPCR, test which checks for a virus in the blood.
  • PortA medical appliance inserted under the skin to allow easy access for inserting a needle.
  • Portal HypertensionHigh blood pressure in the portal vein, may occur due to scarring of the liver or a blockage of the portal vein.
  • Portal VeinMain vein carrying blood from the intestine to the liver.
  • ProteinComplex organic compunds found in the body and in foods such as meat and eggs. Consist mainly of amino acids. They serve a number of functions including as enzymes and are involved in oxygen transport and muscle contraction. As a fuel, proteins contain 4 calories (kcal) per gram, just like(...)
  • ProximalThe opposite of distal. These are the muscles closest to the midline; the central part of the body. Pompe: often there is weakness of the limb girdle, this too is a part of the central core of the body.
  • PruritusItching of the skin.
  • PulmonaryOf the lungs.
  • RenalOf the kidneys.
  • RespiratoryRelated to breathing.
  • RhabdomyolysisThe destruction of cells in the skeletal muscles. In McArdle disease this arises from fixed spasm of the muscle caused by excessive activity such as lifting something heavy - see "anaerobic".
  • SclerotherapyTreatment for varices where a solution is injected into them during an endoscopy.
  • ScreeningTesting for the presence of condition or the genes for a condition.
  • SOS BraceletA bracelet available to buy containing your personalised medical information and emergency contact numbers.
  • Spider NaeviSmall, broken veins under the skin which can look like red spiders.
  • SpleenAn organ which removes old blood cells. Its blood supply is connected to the liver.
  • SplenomegalyEnlarged spleen.
  • Split bilirubin testBlood test which measures how much conjugated and unconjugated bilirubin is in the blood.
  • ThrombosisBlood clot in a vein or artery.
  • TPRAbbreviation for temperature, pulse and respiration.
  • TracheostomyA surgically inserted tube placed in the windpipe which can be connected to an oxygen supply and mechanical ventilator.
  • TriglyceridesType of fat.
  • UK diagnosed Our figures for the number of people diagnosed in the UK with each GSD are our best estimates. These are based on: • Various incidence rates published by medical sources. • An AGSD-UK audit of English NHS specialist centres. • Our own figures from members and people registered with us.• Our(...)
  • Ultrasound scanUSS, scan which takes images of organs and blood vessels.
  • VaricesVeins in the intestine, oesophagus and stomach which can be enlarged and swollen due to portal hypertension. May bleed if not treated.
  • Viral loadA lab test that measures the number of virus particles in a millilitre of blood.
  • XanthomasCholesterol deposited under the skin, can look like pale warts.