The Mucopolysaccharidoses and
Mucolipidoses Treatment Program
Under the direction of medical geneticist Barbara K. Burton, MD, the
Mucopolysaccharidoses and Mucolipidoses Treatment Program provides comprehensive
care and assists patients and families in the management of these complex
conditions. The program's mission is to maximize the quality of life of our
patients by providing outstanding, compassionate care.
What are mucopolysaccharidoses?
Mucopolysaccharidoses (MPS) are a group of genetic disorders each of which is
caused by the deficiency of an enzyme (a protein that produces chemical
reactions in the body) that breaks down one or more types of
mucopolysaccharides, also referred to as glycosaminoglycans (GAGs). GAGs are
long, repeating chains of complex sugar molecules that are normal chemical
components of bones, cartilage, and many other tissues within the body. They are
constantly being “turned over,” meaning that new GAGs are produced as others are
broken down. If the GAGs cannot be broken down normally, they accumulate in
excess in various tissues of the body resulting in the clinical features
associated with an MPS disorder.
Changes in specific genes result in the deficiency or absence of the enzyme.
The MPS disorders are categorized into several groups based on the clinical
features and specific enzyme deficiency. An individual is usually suspected of
having an MPS disorder after developing characteristic physical findings. The
diagnosis is further confirmed by laboratory testing. Clinical features of these
conditions may vary depending on the specific diagnosis.
Find more details on the specific MPS disorders in the associated pages in
this section.
What are mucolipidoses?
Mucolipidoses (ML) are a group of genetic disorders in which both
glycosaminoglycans (GAGs) and another group of substances called sphingolipids
build up in the body. GAGs are long, repeating chains of complex sugar
molecules, and sphingolipids are fats. ML disorders may also be referred to as
“targeting defects” because affected individuals are lacking the enzyme (a
protein that produces chemical reactions in the body) that “targets” other
enzymes to the lysosome (a sac-like structure found in a cell).
ML disorders are different from mucopolysaccharidoses (MPS). In MPS, the
absence or deficiency of one specific enzyme results in an excess of sugars or
GAGs in an individual's tissues and in the urine. In ML, individuals are lacking
multiple enzymes in their lysosomes within their cells because of this targeting
defect.
Changes in specific genes results in the deficiency or absence of the
targeting enzyme. The ML disorders are categorized into four groups based on the
clinical features and enzyme deficiencies. ML-II and ML-III are the more
common forms of ML. An individual is usually suspected of having an ML disorder
based on clinical features. The diagnosis is further confirmed by laboratory
testing.
Carrier testing and prenatal testing for MPS and ML
Prenatal diagnosis is available for all MPS and ML disorders. Amniocentesis
(a procedure in which amniotic fluid is taken from around the fetus) can be used
to obtain fetal cells which are then cultured and used for enzyme analysis or
genetic testing by DNA analysis. In addition, chorionic villus sampling (the
extraction of a small sample of tissue from the developing placenta) can be
performed in the first trimester of pregnancy in order to make a diagnosis.
Pre-implantation genetic diagnosis is possible in some cases, using in vitro
fertilization, if the mutation or mutations responsible for the disorder in a
family have previously been identified. Carrier testing for MPS and ML disorders
can usually be accomplished, either by enzymatic or molecular (DNA-based)
analyses, depending on the specific circumstances.