Dialog Box


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 lacking in individuals with Sanfilippo Type B (MPSIIIB).


Antibodies: Large Y-shaped proteins produced by cells in the blood.  The immune system uses them to identify and neutralise invaders such as viruses and bacteria. Also called immunoglobulins.


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 coies 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. 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 below) 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.

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 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 the 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: Treatmentof 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 N-sulfatase: The enzyme that is lacking in individuals with Sanfilippo Type A (MPS IIIA).

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

Hurler Syndrome: See MPS I


Hunter Syndrome: See MPS II

Immune Response: In regard to lysosomal disease, immune responses refer to the patients development of antibodies which neutralise the proteins administered to them as enzyme replacement therapy (ERT). Such immune responses can largely nullify the therapeutic benefits of ERT in any patient who has developed them. 

Incidence: Refers to the measure of the probability of occurrence of a given medical condition in a population within a specified period of time. 

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; lightheadedness; 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, such as in a person’s 

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.

Lysosomal Enzyme: A protein found within the cytoplasm of most cells, especially leukocytes, kidney and liver cells, which are key components in the function of digestive processes within the cell.

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: A compound involved in circadian rhythms sometimes used as a sleep aid for those with MPS and related diseases.

ML II: Also called I-Cell Disease, caused by a deficiency of the lysosomal enzyme N-acetylglucosaminyl-1-phosphotransferase. Autosomal recessive disease characterized by severe psychomotor retardation and by many of the clinical features seen in severe MPS I.

ML III: Also called Pseudo-Hurler Polydystrophy, caused by a deficiency of the lysosomal enzyme N-acetylglucosaminyl-1-phosphotransferase. Autosomal recessive disease with less severe disease course than ML II, presenting later in life, with survival into adulthood.

Morquio Syndrome: See MPS IV

Mouse model: Mouse modelling refers to the experimental use of mice who 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 absolutely essential role in the development of treatments for these diseases.

MPS I: Also called Hurler, Hurler-Scheie and Scheie, caused by a deficiency of thelysosomal enzyme -L-Iduronidase. Autosomal recessive, heterogeneous disease characterised by a wide range of clinical involvement, including corneal clouding, bone changes, stiff joints, large liver and spleen, and heart disease.

MPS II: Also called Hunter Syndrome, caused by a deficiency of the lysosomal enzyme. Iduronate sulfatase. X-linked recessive, heterogeneous disease characterized by a wide range of clinical involvement, including large liver and spleen, stiff joints, bone changes, and heart disease.

MPS III: Also called Sanfilippo Syndrome, an autosomal recessive disease classified into 4 types based on the enzyme deficiency. The features in each type are similar and characterized by severe central nervous system degeneration but only mild somatic (relating to the body) problems. It was named after its discoverer, the late Dr. Sylvester Sanfilippo at the university of Minessota. 


MPS III-A: Caused by a deficiency of the lysosomal enzyme heparan N-sulfatase.

MPS III-B: Caused by a deficiency of the lysosomal enzyme -N-acetylglucosaminidase.

MPS III-C: Caused by a deficiency of the lysosomal enzyme acetyl CoA: -glucosaminide acetyltransferase.

MPS III-D: Caused by a deficiency of the lysosomal enzyme N-acetyl glucosamine 6-sulfatase.

MPS IV: Also called Morquio syndrome, autosomal recessive disease classified into 2 types based on the enzyme deficiency, each with a wide range of clinical manifestations. Both types are characterised by short trunk dwarfism, fine corneal deposits and preservation of intelligence.

MPS IV-A: Caused by a deficiency of the lysosomal enzyme galactose 6-sulfatase.

MPS IV-B: Caused by a deficiency of the lysosomal enzyme -galactosidase.

MPS VI: Also called Maroteaux-Lamy syndrome, caused by a deficiency of the lysosomal enzyme arylsulfatase B. Autosomal recessive disease with bone abnormalities, corneal clouding and normal intelligence.

MPS VII: Also called Sly Syndrome, caused by a deficiency of the lysosomal enzyme -

Mucolipidosis: Term coined to denote diseases that combined clinical features common to both the mucopolysaccharidoses and the sphingolipidoses (diseases characterized by abnormal lipid or
fat metabolism, affecting nerve tissue). See ML II and ML III

Mucopolysaccharide: A complex carbohydrate molecule that is a common constituent of secretions and the connective tissue between cells. Although the molecules were originally called "mucopolysaccharides" because of their ability to form viscous, mucin-like solutions, the terminology was revised to "proteoglycans" and subsequently to "glycosaminoglycans" in the last decades.

Mutation: A change in the genetic material (DNA) of a cell that alters expected genetic processes.

N-acetylglucosamine 6-sulfatase: Lysosomal enzyme deficient in MPS III-D.

N-acetylglucosaminyl-1-phosphotransferase: Lysosomal enzyme deficient in ML II and ML III.

Neurodegeneration: Neurodegeneration refers to progressive loss of neuronal health and function, and can result in neuron death. Neurodegeneration characterises many conditions/disease found in humanity including many of the lysosomal diseases. 

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 the FDA or another regulatory agency as a baseline to show the agency the disease course for untreated patients.

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

Pseudo-Hurler Polydystrophy: See ML III

Autosomal recessive: A pattern of inheritance requiring the presence of two copies of a particular gene mutation in order to have express clinical signs and symptoms of a condition. Pattern of inheritance seen in all MPS diseases with the exception of MPS II.

X-linked recessive: A mode of inheritance in which a mutation in a gene on the X chromosome causes males to have clinical features of a particular condition as they only have one X chromosome. Pattern of inheritance seen in MPS II.

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 of individuals who provide information relating to their disease or condition of interest, so that research can be more efficiently, effectively and sufficiently 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: A cell whose daughter cells may differentiate into other cell types.

Substrate Reduction Therapy: Substrate Reduction Therapy is a treatment approach for some glycogen storage diseases and other lysosomal storage disorders, in which a critical failure in a metabolic pathway prevents cellular breakdown and disposal of some large molecule. Substrate reduction therapy aims to reduce the amount of the substrate to a level where residual enzyme activity may be sufficient to prevent significant substrate accumulation. 

Swallowing study:  (modified barium swallow study): 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: In a medical research context, it aims to ‘translate’ finding in fundamental research into medical practice and meaningful health outcomes.