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Sanfilippo Glossary

When a child is first diagnosed, parents and caregivers go on a steep learning curve, learning medical terminology to help fully understand their child’s condition. This typically occurs at a time of extreme stress.  This handy glossary contains common words relating to MPS III Sanfilippo Syndrome. 

AAV: Adeno-Associated Virus, a small harmless virus that is used to deliver gene therapies. Also sometimes called a 'vector'. See Gene Therapy


Activities of Daily Living (ADL): The routine activities that people tend to do every day without needing assistance. There are six basic ADLs: eating, bathing, dressing, toileting, transferring (walking) and continence.


Adenoids: The collection of lymphatic tissue atthe rear of the nose. Enlargement of the adenoids may cause obstruction of breathing through the nose. This is common in children with MPS and surgery is often needed to remove them.


Alpha-N-acetylglucosaminidase (NAGLU): The enzyme that is deficient in individuals with Sanfilippo Type B (MPSIIIB).


Atrophy: A wasting of tissues, organs, or the entire body.


Autosomal Recessive Inheritance: A pattern of inheritance where both parents have one copy of the altered gene and one normal copy -- they are known as carriers and do not show signs of the condition. A child with MPS III inherits two copies of the altered gene, one from each parent. The risk is the same for males and females. 


Blood-Brain-Barrier: A barrier that separates the fluid of the brain from the blood circulating in the rest of the body. This barrier is highly selective and only allows certain molecules through to the brain in order to protect this important organ. Therapies to treat conditions that affect the brain, like Sanfilippo, need to be able to cross this barrier or be delivered directly into the brain.


Carpal Tunnel Syndrome:  numbness, tingling and/or weakness of the hand caused by pressure on nerves that run through the wrist. Carpal tunnel syndrome sometimes develops in children with Sanfilippo which requires surgery. 

Carrier: An individual who has one copy of a genetic change in their DNA that is recessive (see autosomal recessive above) and disease causing. Carriers of a recessive condition do not have clinical signs and symptoms of the
condition but if their partner is a carrier of the same condition there is a one in four chance that their offspring will inherit two copies of the faulty gene – one from each parent – and develop the condition.


Central Nervous System (CNS): Consists of the brain and spinal cord, controlls all bodily function.

Cerebrospinal Fluid (CSF): The fluid that surrounds the brain and spinal cord and that is produced in the ventricles of the brain.

Contracture: Muscle shortening resulting in loss of motion of the joint.

Cornea: The transparent circular part of the front of the eye.

Corneal Clouding: Disruption of the clear layers of the cornea in individuals with MPS due to storage of GAG, causing a milky appearance of the eye, decreased vision, and sensitivity to light. Cloudy corneas can be replaced via a corneal transplant. 


DNA: The molecule which encodes the genes responsible for the structure and function of an organism and allows for transmission of genetic information to the next generation

Efficacy: The effectiveness of a particular treatment.  


Enzyme: Proteins that speed up the rate of a chemical reaction in a living organism. For example, enzymes help break down larger molecules of starch, fat, and a protein during digestion.

Enzyme Replacement Therapy: A therapeutic approach for a genetic disease whereby the missing protein is manufactured in a laboratory and injected into the patient on a regular basis.

GAG: The abbreviation for 'glycosaminoglycans' -- complex sugar molecules naturally produced by the body. GAGs are also sometimes called 'mucopolysaccharides'. People with mucopolysaccharidosis conditions such as Sanfilippo do not produce adequate enzymes required to break down these sugar chains and over time they accumulate in the cells of the body. 

Gastrostomy (G-Tube): A surgical procedure in which an opening is made into the stomach from the outside. It is usually performed to allow nutrition and/or medications to be administered directly into the stomach when swallowing is difficult because of disease or obstruction of the oesophagus.

Gene: Genes are made of DNA and each carries instructions for the production of a specific protein. Genes usually come in pairs, one inherited from each parent. They are passed on from one generation to the next, and are basic units of inheritance. Any alterations in genes (mutations) can cause inherited disorders. 

Genetic Counselling: Information and support provided by a certified genetic counsellor to people who have a genetic condition in their family or are concerned about a genetically transmitted condition.

Gene Therapy: Treatment of a disease by introducing a new gene into a cell. The new gene may be used to replace a function that is missing because of a defective gene. Viruses are often used to deliver the new gene into the cells. 

Glycosaminoglycans: See GAGs.


Heparan-apha-glucosaminide N-Acetyltransferase (HGSNAT):  The enzyme that is lacking in individuals with Sanfilippo type C (MPS III C).

Heparan N-sulfatase: The enzyme that is lacking in individuals with Sanfilippo Type A (MPS III A).

Heterogeneity: Variations in clinical features (characteristics) within a specific disease.

Hurler Scheie Syndrome: See MPS I

Hunter Syndrome: See MPS II

Immune Response: How your body recognises and defends itself against bacteria, viruses and substances that appear foreign and harmful. In regards to therapies for lysosomal disease, immune responses refer to the patient's development of antibodies which neutralise either enzyme replacement therapy (ERT) or gene therapy given to them.

Incidence: Incidence is the rate of new (or newly diagnosed) cases of a disease. It is generally reported as the number of new cases occurring within a period of time (e.g. per month, per year). It is more meaningful when the incidence rate is reported as a fraction of the population at risk of developing the disease (e.g.  per 100,000 or per million population).

Incubator research grants: Grants that provide seed funding for the early stages of innovative research grants with the aim of generating preliminary data needed to support future grant applications.

Infantile onset: The onset of disease that begins during the first two years of life.

Infusion related reaction: Infusion-related reactions are some patients’ responses to receiving intravenous administration of a treatment such as enzyme replacement therapy. These reactions might including flushing of the skin; fever; chills; dizziness; light-headedness; fainting; shortness of breath; difficulty breathing; or fast, irregular or pounding heartbeat. These reactions can occur at the time of infusion or be delayed by hours or days. 

Late onset: Onset of the disease later in life  than usual. For example, symptoms of Sanfilippo usually appear in early childhood but some individuals have late onset forms of the condition that appear in the teen years.

Lumber Puncture: A procedure in which cerebrospinal fluid is withdrawn by means of a needle inserted into the membrane space in the region of the lower back. This procedure may be performed to measure intracranial pressure to aid in diagnosing hydrocephalus (fluid accumulation in the brain) or to measure the level of enzymes in a patient's cerebrospinal fluid.

Lysosomal Enzyme: A protein found within a compartment of the cell called the lysosome that breaks down food molecules, especially proteins and complex sugar molecules.

Lysosomal Storage Disease (LSD): An inborn error of metabolism resulting in a particular lysosomal enzyme deficiency. At this time there are more than 40 identifiable lysosomal storage diseases.

Lysosome: A specialised compartment (organelle) in the cytoplasm of cells that contains enzymes responsible for breaking down substances in the cell.

Melatonin:  Melatonin is a hormone naturally produced by the body's pineal gland, a small gland in the brain to help control the body's circadian rythms (sleep and wake cycles). Very small amounts are found in foods and it is available as a supplement. Melatonin is sometimes used as a sleep aid for those with MPS and related diseases.

Morquio Syndrome: See MPS IV

Mouse model: Mouse modelling refers to the experimental use of mice that have been bred to have a specific disease or condition of interest for purposes of medical research. For example, mouse models of lysosomal diseases play an essential role in the development of treatments for these diseases.

MPS I: Also called Hurler, Hurler-Scheie and Scheie,  a type of MPS caused by a deficiency of the lysosomal enzyme alpha-L-iduronidase. A condition with a wide range of severity and affecting many parts of the body including the brain, eyes, bones, joints, liver, spleen, and heart.

MPS II: Also called Hunter Syndrome, a type of MPS caused by a deficiency of the lysosomal enzyme iduronate sulfatase.  A condition that occurs almost exclusively in males and affects many parts of the body including the liver, spleen, joints, bones and heart.

MPS III: Also called Sanfilippo Syndrome, a progressive disorder that primarily affects the brain and spinal cord (central nervous system). Other body systems can also be involved. Classified into four types based on the enzyme deficiency. It was named after its discoverer, the late Dr. Sylvester Sanfilippo at the University of Minessota. 







heparan N-sulftase






heparan-alpha-glucosaminide N-acetyltransferase



N-acetylglucosamine 6-sulfatase


MPS III A: Sanfilippo Syndrome caused by a deficiency of the lysosomal enzyme heparan N-sulfatase. Also called Sanfilippo type A.

MPS III B: Sanfilippo Syndrome caused by a deficiency of the lysosomal enzyme alpha-N-acetylglucosaminidase. Also called Sanfilippo type B.

MPS III C: Sanfilippo Syndrome caused by a deficiency of the lysosomal enzyme hepar-alpha-N-acetyltransferase. Also called Sanfilippo type C.

MPS III D: Sanfilippo Syndrome caused by a deficiency of the lysosomal enzyme N-acetylglucosamine 6-sulfatase. Also called Sanfilippo type D.

MPS IV: Also called Morquio Syndrome, a type of MPS that is classified into two types based on the enzyme deficiency, each with a wide range of symptoms including abnormal development of bones, short stature, large head and hypermobile joints. Breathing, heart and vision problems may develop but cognitive function is usually normal.


MPS VI: Also called Maroteaux-Lamy Syndrome, a progressive condition that causes many tissues and organs to enlarge and become inflamed or scarred. Skeletal abnormalities are also common in this condition.

MPS VII: Also called Sly Syndrome, is a progressive condition that affects mosts tissues and organs. The severity of MPS VII varies widely among affected individuals.

Mucolipidosis (ML): A group of inherited metabolic diseases similar to the MPS group of diseases that affect the body's ability to carry out the normal turnover of various materials within cells.  In ML, abnormal amounts of carbohydrates and fatty materials (lipids) accumulate in cells. There are two types - ML II and ML III that are also called I-Cell Disease and Pseudo-Hurler Polydystrophy.

Mucopolysaccharide: complex sugar molecules naturally produced by the body and used in the building of bones, cartilage, skin and tissues. Mucopolysaccharides get their name from their thick jelly-like consistency ('muco'), 'poly' meaning many and 'saccharide' meaning sugar. Also called glycominoglycans (GAGs).

Mutation: A change in the DNA that alters the genetic message carried by that gene.

N-acetylglucosamine 6-sulfatase: the enzyme that is lacking in individuals with Sanfilippo type D (MPS III D).

Neurodegeneration: Progressive deterioration of the nervous system, especially of neurons in the brain. This deterioration gradually causes a loss of cognitive abilities such as memory and decision-making. Neurodegeneration characterises many conditions/disease found in humanity including many of the lysosomal diseases, as well as more common conditions such as Parkinsons and Alzheimers.

Natural History Study (NHS): In medicine, a natural history study is a study that follows a group of people over time who have, or are at risk of developing, a specific medical condition or disease. A natural history study collects health information to understand how the medical condition or disease develops and to give insight into how it might be treated. A natural history study is often submitted when applying to regulatory agency (such as the FDA in the US or TGA in Australia) as a baseline to show the agency the disease course for untreated patients.

Newborn screening: is the collection and analysis of a newborn baby’s blood to rule out the presence of certain hereditary diseases.  

Recombinant DNA: DNA that contains genes from different sources that have been combined by the techniques of genetic engineering.

Registry: In regard to healthcare, a registry is a database containing relevant information about individuals with a particular disease or condition so that research can be more efficiently and effectively conducted.


Sanfilippo Syndrome: See MPS III

Scheie Syndrome: Mild end of a clinical spectrum of MPS I. See MPS I

Seizure: Disruption of electrical signals in the brain. Seizures may cause brief changes in a person’s body movements, awareness, emotions or sense such as taste, smell, vision, or hearing.

Sly Syndrome: See MPS VII

Small molecules:  In the context of treating rare diseases, small molecules are those that are not large macromolecules (such as proteins) and are often more likely to cross the blood brain barrier (BB)

Stem Cells: One of the human body's master cells, with the ability to grow into any one of the body's more than 200 cell types.

Substrate Reduction Therapy: A treatment approach for some lysosomal storage disorders, in which a drug limits the production of the substrate which is not degraded and therefore accumulates. For example, in Sanfilippo the aim would be to limit the production of the of GAGs (which is the substrate) so there is less to accumulate in the cells.

Swallowing study: (modified barium swallow study): A videotaped X-ray of an individual’s oral (mouth) and pharyngeal (throat) mechanism during eating or drinking. This procedure is often ordered to evaluate for obstruction or aspiration. The results from this procedure may allow for a therapist to better identify ways to safely feed the individual and ways to help the family make appropriate modifications.

Translational research: Research that aims to 'translate' findings in the laboratory into medical practice and meaningful health outcomes.