Here is a glossary of the main medical terms for families. This does not replace the advice of a doctor. Currently only available in French.

Allele An allele is one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent.
Anaemia Anaemia is a blood disorder that affects the quantity and quality of red blood cells in the blood. It may be due to a deficit of iron.
Audiogram An audiogram is a graph that shows the softest sounds a person can hear at different pitches or frequencies.
Autosomal recessive Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families. An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop.
Basic research Basic medical research studies the mechanisms of normal and pathological processes.
Biotherapy All treatments based on the use of organisms or substances derived from living matter (such as microbes, genes, cells, tissues, organs) to stimulate or restore the body’s ability to fight a disease.
Bone marrow transplant Refer to the site of the Foundation under the tab " Sanfilippo syndrome"
Carbohydrates Carbohydrates are a class of organic molecules comprising only carbon, hydrogen, and oxygen, usually with a hydrogen:oxygen atom ratio of 2:1 . The term is most common in biochemistry, where it is a synonym of saccharide.
Catalyst A substance, usually used in small amounts relative to the reactants*, that modifies and increases the rate of a reaction without being consumed in the process.
* substance that is consumed in the course of a chemical reaction.
Cell A cell is the basic element of the building of a living being. The body is made ​​up of billions of cells with very different functions: skin cells, neurons, white and red cells. Most of these cells have relatively similar structures. They consist of:
  • a particular nucleus that contains the genetic material of an individual in the form of 23 pairs of chromosomes, each chromosome containing a long DNA molecule,
  • a cell membrane that surrounds the cell and regulates all trade between the contents of the cell and the outside,
  • the cytoplasm which is a kind of liquid in the interior of the cell and which contains different organelles (see organite or organelle below). These organelles provide all functions that are necessary to the life of the cell.
Cell therapy Its aim is to introduce new cells into a tissue in order to restore its deficient biological functions.
Chemical chaperone See the Foundation's website under « Sanfilippo syndrome ».
Clinician Physician who makes a diagnosis by direct examination of patients (as opposed to one engaged in laboratory or experimental studies).
Connective tissue Tissue supporting organs and filling spaces between them.
Cystinosis Cystinosis is a condition related to a defective transport of cystine out of lysosomes resulting in lysosomal accumulation of cystine (2 amino acid cysteine linked together) in different organs. The degradation product of the amino acid cystine ​​is used in the treatment of cystinosis under the trade name Cystagon.
Cytoplasm (See lysosome below)
Enzyme A protein that acts as a biological catalyst. It facilitates biochemical reactions without altering the products. It is capable of lowering the activation energy of a reaction and thus speeding up millions of times the chemical reactions of metabolism without altering it.
Enzyme deficiency When both copies of a gene coding for a lysosomal enzyme are inactivated by mutation, the process of lysosomal digestion within the cell is disrupted and molecules that are not digested by enzymes accumulate in lysosomes. The number and the size of lysosomes increase in the cell, causing an anomaly of functioning of the latter, even its death. This mechanism is responsible for the appearance of the symptoms of lysosomal diseases.
The lysosomal diseases are numerous, and appear in very different wasy:
  • they affect, as the case may be, different organs;
  • they can be mild or very severe;
  • they can appear very early in life or only in adulthood;
  • the same lysosomal disease differs as every patient is different.
Enzymotherapy (or enzyme therapy) Use of enzymes for therapeutic purposes.
Enzyme replacement therapy The aim of this therapy is to replace the missing or deficient enzyme by a “recombinant” enzyme, produced through biotechnological processes.
Epidemiology Study of different factors involved in the onset and progression of one or more diseases.
Eucaryote Living body possessing an isolated nucleus. Genetic material in eukaryotes is contained within the nucleus.
Fabry disease Fabry disease is a hereditary pathology of the metabolism of glycosphingolipids, recessive transmission bound to the X chromosome, due to the deficit in a lysosomal enzyme: the alpha-galactosidase A. The enzymatic defect leads to the accumulation of the substratum not degraded in tissues and plasma. In its classic shape, the disease affects more severely hemizygotes (men), to whom the clinical signs begin in the childhood with pains of the extremities and dermatological signs. Heterozygous women are often symptomatic but in a more variable way and generally less affected than men. The diagnosis is definitively confirmed by the dosage of the enzymatic activity for men and the search for the mutation of the gene GLA for the women. *Author: Dr D. Germain (September, 2002) *. Replagal ® (agalsidase alpha), produced by Shire (Cambridge, Massachusetts) is used for the treatment of the disease of Fabry.
Family multiplex A family is called multiplex when several members of the family are affected by a disease.
Gaucher’s Disease Gaucher's disease occurs when certain harmful fatty substances accumulate to excessive levels in the liver, spleen, lungs, bone marrow and, less commonly, brain. This accumulation of fatty material in tissues interferes with how the body works and may cause organ enlargement and bone pain. Gaucher's disease is caused by a deficiency of the enzyme « glucocerebrosidase », which helps the body process the fatty substance called glucocerebroside. The disease is sometimes called glucocerebrosidase deficiency (Definition by Mayo Clinic.)
Gene therapy Gene therapy consists in replacing the defective or missing gene by a correct version of this gene or by stimulating the over-expression of a protein that could have therapeutic impact.
Genetic cause The parents of an individual with an autosomal recessive condition carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
MPS IIIA is caused by mutations in the SGSH gene, and MPS IIIB is caused by NAGLU gene mutations. Mutations in the HGSNAT gene result in MPS IIIC, and GNS gene mutations cause MPS IIID. Mutations in these genes reduce or eliminate enzyme function. A lack of any one of these enzymes disrupts the breakdown of heparan sulfate. As a result, partially broken down heparan sulfate accumulates within cells, specifically inside the lysosomes. Lysosomes are compartments in the cell that digest and recycle different types of molecules. Conditions such as MPS III that cause molecules to build up inside the lysosomes are called lysosomal storage disorders. Researchers believe that the accumulation of GAGs interferes with the functions of other proteins inside the lysosomes and disrupts the normal functions of cells. It is unknown why the buildup of heparan sulfate mostly affects the central nervous system in MPS III. Source :
Genotype All genetic constituents of an individual.
Glucides Commonly known as "sugars" and scientifically referred to as "carbohydrates",glucides are quick-energy ingredients. They circulate in the blood in the form of glucose which is immediately used in cellular combustion. If the glucose concentration is too high as compared to the current energy needs, it is temporarily stored in the liver or in the muscles in an agglutinated form called glycogen.
Glucosamine Nombre de nouveaux cas apparus pendant une année au sein d'une population.
Glycosamoniglycan (or GAG) Glycosaminoglycans or mucopolysaccharides are long unbranched polysaccharides consisting of a repeating disaccharide unit. Mutations in the GNS, HGSNAT, NAGLU, and SGSH genes cause MPS III. These genes provide instructions for making enzymes involved in the breakdown of GAGs. The GNS, HGSNAT, NAGLU, and SGSH enzymes are involved in the step-wise breakdown of a subset of GAGs called heparan sulfate.
Read more:
GNS The product of this gene is a lysosomal enzyme (N-acetylglucosamine-6-sulphate sulphatase) found in all cells. It is involved in the catabolism of heparin, heparan sulphate, and keratan sulphate. Deficiency of this enzyme results in the accumulation of undegraded substrate and the lysosomal storage disorder mucopolysaccharidosis type IIID (Sanfilippo D syndrome). Mucopolysaccharidosis type IIID is the least common of the four subtypes of Sanfilippo syndrome. (provided by RefSeq, Jul 2008).
Healthy carrier (inactive carrier or asymptomatic carrier) A person who carries an infectious agent but never fall ill or manifests no evidence that he/she is infected.
Hereditary disease Genetic disease that is transmitted from generation to generation.
Heterozygote An individual who has two different forms of a particular gene, one inherited from each parent.
HGSNAT This gene encodes a lysosomal acetyltransferase, which is one of several enzymes involved in the lysosomal degradation of heparin sulfate. Mutations in this gene are associated with Sanfilippo syndrome C, one type of the lysosomal storage disease mucopolysaccaridosis III, which results from impaired degradation of heparan sulfate. (provided by RefSeq, Jan 2009)
Homozygote An individual who as two similar forms of a particular gene.
Hunter syndrome Hunter syndrome is due to a deficit of iduronate 2-sulfatase ( IDS). The accumulated substrate in Hunter syndrome is heparan sulfate and dermatan sulfate.
Hurler syndrome Hurler syndrome is due to a deficit in alpha-L-iduronidase. This disease benefits from enzyme replacement therapies (BioMarin manufactures laronidase = Aldurazyme, commercialized by Genzyme Co.)
Hydrolase An enzyme that speeds up the process of hydrolysis.
Incidence Number of new cases of a disease in a year in a given population.
Inhibition of substrate As the substrate for the defective enzime accumulates in the lysosome, it leads to cellular disfunction. The purpose of the inhibition of substrate aims to reduce the synthesis of GAG chains, the natural substrate for the deficient enzyme.
Read more :
Intrathecal administration Direct introduction into the cerebrospinal fluid by injection into the space surrounding the spinal cord in order to bypass the blood-brain barrier.
Lysis The dissolution of a cell, a bacterium, by destroying its membrane with a chemical substance.
Locus The precise place where is situated a gene (or a series of genes) on a chromosome.
Lysosomal diseases (see also enzyme deficiency) Lysosomal diseases are due to a malfunction of a lysosomal enzyme, which prevents cells from performing their natural recycling function.
Lysosome A particle in the cytoplasm of cells containing a number of digestive enzymes capable of breaking down most of the constituents of living matter. (The cytoplasm consists of all of the contents outside of the nucleus and enclosed within the cell membrane of a cell).
Maroteaux-Lamy syndrome The syndrome of Maroteaux-Lamy is characterized by dwarfism, deafness and progressive deformations of the skeleton. It is the result of the missing enzyme (arylsulfatase B), which normally breaks down the mucopolysaccharides dermatan sulfate. It is treated by Naglazyme ®.
Metabolism All transformation reactions that occur in the body. Metabolism includes two major processes: anabolism which is the set of reactions leading to synthesis and catabolism, which is the set of reactions leading to degradation and/or release of energy.
Metabolite Compound stemming from the biochemical transformations produced during metabolism.
Monomer In biology, a monomer is the constitutive element of polymers, as proteins (e.g. haemoglobin and albumin), nucleic acids (e.g. DNA) and polysaccharides (e.g. mucopolysaccharides).
Morquio disease Morquio disease is caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase enzyme. Recombinant enzyme therapy is currently being developed.
Mucopolysaccharides (synonym of glycosamoniglycans) Mucopolysaccharides are long chains of sugar molecules that are found throughout the body, often in mucus and in fluid around the joints. Source:
Mucopolysaccharidosis One of a series of inherited metabolic disorders affecting a type of complex carbohydrate called a mucopolysaccharide that is deposited in body tissues as the person lacks the specific enzyme needed to metabolize it.
The classification (as of 2001) is as follows:
  • MPS type I -- Hurler syndrome, Scheie* syndrome, and Hurler-Scheie syndrome -- due to varying degrees of deficiency of the enzyme alpha-L-iduronidase
  • MPS type II -- Hunter syndrome -- due to deficiency of the enzyme iduronate sulfatase
  • MPS type IIIA -- Sanfilippo syndrome -- due to deficiency of the enzyme heparan N-sulfatase
  • MPS type IIIB -- Sanfilippo syndrome -- due to deficiency of the enzyme alpha-N-acetylglucosaminidase
  • MPS type IIIC -- Sanfilippo syndrome -- due to deficiency of the enzyme acetyl CoA:alpha-glucosaminide acetyltransferas
  • MPS type IIID -- Sanfilippo syndrome -- due to deficiency of the enzyme N-acetylglucosamine 6-sulfatase
  • MPS type IVA -- Morquio A syndrome -- due to deficiency of the enzyme N-acetylgalactosamine-6- sulfatase
  • MPS type IVB – Morquio B syndrome -- due to deficiency of the enzyme beta-galactosidase
  • MPS type V – Scheie syndrome – due to deficiency of the enzyme alpha-L-iduronidase
  • MPS type VI -- Maroteaux-Lamy syndrome -- due to deficiency of the enzyme N-acetylgalactosamine-4-sulfatase
  • MPS type VII -- Sly syndrome -- due to deficiency of the enzyme beta-glucuronidase
  • MPS type VIII -- DiFerrante syndrome -- due to deficiency of the enzyme glucosamine-6-sulfate
  • MPS IX - The disorder results from hyaluronidase deficiency
Source :
Multiplex family A family in which several family members are affected by the disease.
NAGLU This gene encodes an enzyme that degrades heparan sulfate by hydrolysis of terminal N-acetyl-D-glucosamine residues in N-acetyl-alpha-D-glucosaminides.
Natural history Description of the different manifestations of a disease and their evolution over time in the absence of any treatment.
Niemann-Pick diseases Niemann-Pick Types A and B, are caused by the deficiency of a specific enzyme, acid sphingomyelinase (ASM). For research on treatment see:
Organites or organelles The various membrane-bound structures contained in the cytoplasm. Each has have a specific function.
Oses Oses (or monosaccharides) are the monomers of carbohydrates ( e.g. glucose, sucrose, cellulose, etc.)
Phenotype All observable characteristics of an individual. The phenotype is the expression of genes but also of environmental effects.
Phospholipids (see organites)
Physiopathology Study of the physiological changes induced by a disease.
Prevalence The number of people affected by a disease observed at a given time.
Prognosis for survival Forecast of the evolution of a disease toward death.
Protoplasm Constituent of the living cells. It comprises the cytoplasm, the nucleus and the organelles.
Pompe disease Pompe disease is caused by mutations in a gene that makes an enzyme called acid alpha-glucosidase (GAA). The disease of Pump benefits from a treatment called Myozyme ®, produced by Genzyme.
Rare Disease A rare disease is defined by its frequency. A disease is considered rare when it affects less than one over 2000.
Sanfilippo syndrome Sanfilippo syndrome occurs when the enzymes that are needed to break down the heparan sulfate sugar chain are either defective, or missing entirely. Sanfilippo syndrome is a form of inherited disease involving a person’s metabolism. There are 4 types of MPSIII: MPS type IIIA, MPS type IIIB, MPS IIIC, MPS type IIID. New treatments in gene and stem cell therapies that are in development could mean that someday Sanfilippo syndrome will become treatable. Source :
Scheie syndrome Persons with Scheie syndrome are missing a substance called lysosomal alpha-L-iduronidase. Enzyme replacement therapy for patients with a defect in the enzyme a-L-iduronidase is now possible. This includes individuals with Scheie syndrome, but also Hurler and Hurler-Scheie syndromes. Source :
SCSH This gene encodes one of several enzymes involved in the lysosomal degradation of heparan sulfate. Mutations in this gene are associated with Sanfilippo syndrome A, one type of the lysosomal storage disease mucopolysaccaridosis III, which results from impaired degradation of heparan sulfate (provided by RefSeq, Jul 2008).
Siblings Brother(s) or sister(s) having one or both parents in common.
Sly syndrome Sly syndrome is caused by a deficiency of the enzyme beta-glucuronidase that leads to an accumulation of dermatan sulfate (DS), heparan sulfate (HS) and chondroitin sulfate (CS) in many tissues and organs of the body including the central nervous system. Bone marrow transplant can be successful. See :
Stem cell Stem cells are undifferentiated or ‘blank’ cells found in the human body that have the potential to develop into many different cell types that carry out different functions. Source :
Translational research Translational research operates the continuum between basic and clinical research. It allows to develop faster therapeutic innovations for the patients benefit.