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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 Deficiency
    Another 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.
  • Acute
    Sudden and severe.
  • Acute renal failure
    ARF, 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 triphosphate
    ATP, a molecule in muscle cells which serves as an energy source for the metabolic process.
  • Aerobic exercise
    Exercise 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 aminotransferase
    ALT, an enzyme produced mainly in the liver. Also known as alanine transaminase.
  • Albumin
    A protein made by the liver. Controls fluid in the blood and tissues.
  • Alkaline phosphatase
    ALP/ALK-PHOS, an enzyme produced in the bile ducts and elsewhere in the body.
  • ALT
    Alanine transaminase (also know as alanine aminotransferase) an enzyme found mostly in the liver. Levels are sometimes higher in people with Pompe disease.
  • Anaemia
    A lack of iron can lead to a person having fewer red blood cells than usual. There can also be other causes.
  • Anaerobic
    Without oxygen. A type of activity which uses stored energy rather than blood-borne energy.
  • Anaerobic exercise
    Exercise 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.
  • Anastomosis
    A connection made surgically between two tubes.
  • Angiogram
    A scan using x-rays to see blood vessels. It can be used to see the blood vessels which supply the liver.
  • Arrythmia
    Irregular rhythm often describing the way the heart beats. This includes; too fast, too slow or fluttering.
  • Ascites
    Fluid collecting in the abdomen.
  • Aspartate aminotransferase
    An enzyme produced mainly in the liver.
  • Atelectasis
    Collapse or closure of a lung.
  • Atresia
    Blocked, destroyed or missing.
  • Atrophy
    Wasting away or degeneration.
  • Autosomal recessive
    One 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).
  • Banding
    Treatment for varices. Surgical elastic bands are placed around the varices during an endoscopy.
  • Bile
    Green/yellow liquid containing bile salts, bilirubin and cholesterol.
  • Bile acids
    Acids found in bile which can be converted into bile salts.
  • Biliary tract
    The system of tubes which carry bile from the liver and gall bladder and drain into the intestine.
  • Bilirubin
    Product 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.
  • Biopsy
    Procedure to take a small sample of tissue to test in the laboratory. In GSDs these are usually from the liver or muscle.
  • BiPaP
    Type 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 Glucose
    Amount of glucose that is in your blood.
  • Body Mass Index
    BMI, a test using height and weight to measure whether an individual is a healthy weight.
  • Cannula
    A short, soft, narrow plastic tube temporarily put into a vein so medicines/fluids/blood etc. can be given intravenously (IV) as needed.
  • Carbohydrate
    A type of compound, such as starches and sugars, found in food. Broken down in the body to form energy.
  • Cardiac
    Of the heart.
  • Cardiomegaly
    Abnormal enlargement of the heart.
  • Cardiomyopathy
    Disease 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 system
    The heart and blood vessels which transport nutrients and oxygen around the body.
  • Cell
    Basic structural and functional component of all living things.
  • Central venous line
    CVL, 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.(...)
  • Cholangitis
    Inflammation or infection of bile ducts which can cause poor bile flow from the liver and liver damage.
  • Cholestasis
    Reduction or blockage of bile flow.
  • Chronic
    An illness or condition which lasts over a period of time.
  • Chronic Hepatitis
    Inflammation of the liver that lasts over a period of time. Liver cells may be destroyed by the inflammation.
  • Coagulopathy
    Any condition where the blood cannot clot properly.
  • Computerised tomography scan
    CT Scan, x-rays are used to create a detailed picture of parts of the body.
  • Congenital
    Condition which is present from birth.
  • CPAP
    A 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 kinase
    Abbreviated 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.
  • CRIM
    Cross 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(...)
  • Cystic
    Relating to the gall bladder
  • Cytomegalovirus
    CMV, a virus belonging to the herpes virus group.
  • Dietician
    A 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.
  • Distension
    Expansion or enlargement.
  • Duct
    Tube which fluid can pass through from one part of the body to another, e.g. bile ducts.
  • DWP
    The 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
  • ECG
    Electrocardiogram. 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.
  • Echocardiogram
    Echo, a scan of the heart using high frequency sound waves, similar to an ultrasound of the abdomen.
  • Electrocardiogram
    The 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.
  • Encephalopathy
    Changes 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.
  • Endoscopy
    Using 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 feeding
    Feeding through a tube directly into the stomach or part of the intestine.
  • Enzyme
    A protein which the body uses to make a chemical reaction happen.
  • Epstein Barr virus
    EBV, a virus which causes glandular fever.
  • ERCP
    Endoscopic retrograde cholangiopancreatography, a special x-ray used to examine bile ducts under general anaesthetic.
  • ERT
    Enzyme Replacement Therapy.
  • ESA
    Employment 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.
  • Faeces
    Also known as stool or poo.
  • Fibrosis
    Scar tissue which replaces normal tissue which, when extensive, is known as cirrhosis.
  • Forbes Disease
    Another name for GSD3 in honour of American clinician Gilbert Burnett Forbes.
  • Full blood count
    FBC, blood test measuring all of the different types of cells in the blood.
  • Fulminant
    Severe, sudden form of liver failure. More commonly known as acute liver failure.
  • GAA
    Lysosomal 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.
  • Gallbladder
    Small sac which stores and releases bile made by the liver.
  • Gallstones
    Stones 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.
  • Gastroenterology
    Study of the digestive system.
  • General anaesthetic
    An individual is put into a state of controlled unconsciousness.
  • Genes
    Made up of DNA and provide instructions for the body.
  • Genome
    All the genes together are called the genome. Each living thing has its own genome, the entire collection of genes.
  • Glucose
    The end product of carbohydrate metabolism and also found in certain foods such as fruit. The chief source of energy.
  • Glycogen
    The 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.
  • Glycolysis
    The 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.
  • Graft
    Organ, tissue or cells used for transplantation.
  • Haematemesis
    Vomiting blood.
  • Haemoglobin
    Part of a red blood cell which carries oxygen around the body.
  • Hepatic
    Of the liver.
  • Hepatic artery
    Blood vessel which brings blood with oxygen to the liver.
  • Hepatic vein
    Blood vessel which takes blood away from the liver.
  • Hepatitis
    Inflammation of the liver.
  • Hepatology
    Study of the liver.
  • Hepatomegaly
    Enlargement of the liver.
  • Hydrotherapy
    Using water as a treatment or therapy. This can be either cold, warm or hot water and often means exercises or movements in the water.
  • Hypertension
    High blood pressure.
  • Hypoglycaemia
    Deficiency of glucose in the bloodstream. Often called low blood sugar. May be associated with symptoms such as anxiety, sweating, tremor, palpitations, nausea, and pallor.
  • Hypotension
    Low blood pressure.
  • Hypotonia
    Poor or low muscle tone, often seen as floppy, weak muscles.
  • Idiopathic
    Something with no known cause.
  • Immunity
    Protection against a particular disease, occurring naturally or due to vaccination.
  • Immunoglobulin
    Protein which plays a role in the immune system.
  • Immunosuppression
    Medications which make the immune system less active.
  • Incidence
    Number of new cases of a disease over a certain period of time in a population.
  • International normalised ratio
    INR, a measure of how well blood clots.
  • Intravenous
    Into the vein. Some fluids and drugs are delivered into the veins.
  • Isometric
    Muscular 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.
  • Jaundice
    High level of bilirubin in the blood leading to yellowing of the skin and/or the whites of the eyes.
  • Kasai portoenterostomy
    Operation 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 acid
    An 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 tests
    LFT, blood tests which can show how well the liver is working.
  • Lymph
    Clear, watery liquid derived from body tissues which carries white blood cells and fats. It travels through the lymphatic system of the body.
  • Lymphadenectomy
    Operation to remove the lymph nodes.
  • Lysosome
    Found inside a cell, they digest or recycle waste from cell metabolism.
  • Malignant hyperthermia
    A 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 disorder
    A condition in which metabolism is affected.
  • Metabolism
    Processes in the body which break down and build up different chemicals in the use of energy. The process simply starts with taking in food.
  • Mitochondria
    A 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 Biopsy
    A medical procedure in which a small piece of muscle is removed from the body and tested.
  • Mutation
    A permanent change or alteration. Can occur within the gene.
  • Myalgia
    Pain in a muscle or muscles. This the main symptom of muscle GSDs.
  • Myoglobin
    A protein found in red skeletal muscle.
  • Myoglobinuria
    Presence 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.
  • Myopathy
    A disease of the muscle.
  • Myophosphorylase
    The muscle type of phosphorylase. Deficient in McArdle disease. There are also brain and neo-natal forms.
  • Nasogastric
    NG feeding, giving food through a tube which goes through the nose and down the throat to the stomach.
  • Nasogastric tube
    Tube used during nasogastric feeding.
  • Nasojejunal tube
    NJ, small tube that is passed up the nose and down the throat, through the stomach, and into the small intestine used for feeding.
  • Natural History
    The 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.
  • Neuromuscular
    Of the muscle and nerves. People with muscle glycogen storage disease may be diagnosed and/or cared for by a neuromuscular consultant.
  • NIV
    Non Invasive Ventilation when air is supplied via a mask over the nose and/or mouth.
  • Occupational Health Therapist
    Provides 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.
  • Oedema
    A build up of fluid in the affected tissues. Also known as fluid retention.
  • Osteopenia
    Bones that are weaker than normal.
  • Parenteral nutrition
    PN, feeding nutrients directly into the vein when an individual cannot eat normally.
  • Percutaneous Transhepatic Cholangiography
    PTC, 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.
  • Phlebotomist
    Person who takes blood samples.
  • Phosphorylase
    An enzyme used in the conversion of stored glycogen to glucose so that it can be utilised for energy.
  • Physiotherapy
    A 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.
  • Platelets
    Part of the blood, important for clotting the blood. Can be low in people with liver disease.
  • Polymerase Chain Reaction
    PCR, test which checks for a virus in the blood.
  • Port
    A medical appliance inserted under the skin to allow easy access for inserting a needle.
  • Portal Hypertension
    High blood pressure in the portal vein, may occur due to scarring of the liver or a blockage of the portal vein.
  • Portal Vein
    Main vein carrying blood from the intestine to the liver.
  • Protein
    Complex 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(...)
  • Proximal
    The 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.
  • Pruritus
    Itching of the skin.
  • Pulmonary
    Of the lungs.
  • Renal
    Of the kidneys.
  • Respiratory
    Related to breathing.
  • Rhabdomyolysis
    The 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".
  • Sclerotherapy
    Treatment for varices where a solution is injected into them during an endoscopy.
  • Screening
    Testing for the presence of condition or the genes for a condition.
  • SOS Bracelet
    A bracelet available to buy containing your personalised medical information and emergency contact numbers.
  • Spider Naevi
    Small, broken veins under the skin which can look like red spiders.
  • Spleen
    An organ which removes old blood cells. Its blood supply is connected to the liver.
  • Splenomegaly
    Enlarged spleen.
  • Split bilirubin test
    Blood test which measures how much conjugated and unconjugated bilirubin is in the blood.
  • Thrombosis
    Blood clot in a vein or artery.
  • TPR
    Abbreviation for temperature, pulse and respiration.
  • Tracheostomy
    A surgically inserted tube placed in the windpipe which can be connected to an oxygen supply and mechanical ventilator.
  • Triglycerides
    Type 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 scan
    USS, scan which takes images of organs and blood vessels.
  • Varices
    Veins in the intestine, oesophagus and stomach which can be enlarged and swollen due to portal hypertension. May bleed if not treated.
  • Viral load
    A lab test that measures the number of virus particles in a millilitre of blood.
  • Xanthomas
    Cholesterol deposited under the skin, can look like pale warts.