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MPS III FACT SHEET
Julie Ann Hall
What is MPS III
MPS III is an inherited disorder that encompasses a wide spectrum of severity. The
brain is the primary site of disease and its function declines with time; physical
symptoms may also develop with time, and may include hearing and breathing
difficulties. The age of onset of symptoms and rate of disease progression vary
considerably; in some, disease progress may be rapid with diagnosis in the first few
years of life. The life expectancy of an individual with MPS varies based on onset.
Some individuals have lived into adulthood but this is usually accompanied by a
decline in their quality of life as brain function deteriorates. MPS III is also referred
to as Sanflippo Syndrome, so named after the doctor who first described the
condition in 1963.
What Are the Major Characteristics of MPS
Mucopolysaccharidoses (MPS) diseases are genetic lysosomal storage diseases (LSD) caused by the body’s
inability to produce specific enzymes. ‘Muco’ refers to the thick jelly-like consistency of the molecules, ‘poly’
means many, and ‘saccharide’ is a general term for the sugar part of the molecule. Mucopolysaccharides are
used by the cells to build connective tissues in the body, such as skin, muscle, cartilage and bone. The human
body is made up of billions of cells. Each cell contains various structures that carry out many functions
important to life; one such structure is lysosome. Mucupolysaccarides carry out their task outside the cell and
once their job is complete they are transported to the lysosomes to be degraded into their basic building blocks.
Degradation requires the action of enzymes that are found inside the lysosomes.
In people with an MPS disorder one of the lysosomal enzymes that is needed to degrade mucopolysaccharides is
either missing or is present at levels that do not allow the recycling process to work properly. As a result, cells
do not perform properly and may cause progressive damage throughout the body, including the heart, bones,
joints, respiratory system and central nervous system.
How is MPS III Inherited
We all have genes inherited from our parents which control whether we are tall, short, fair, etc. Some genes we
inherit are "recessive", that is to say we carry the gene but it does not have any affect on our development. MPS
III is caused by a recessive gene. If the adult carrying the abnormal gene marries another carrier there will be a
one in four chance with every pregnancy that the child will inherit the defective gene from each parent and will
be affected with the disorder. There is a two in three chance that unaffected brothers and sisters of MPS III
patients will be carriers. They can be reassured; however, as the disease is so rare, the chance of marrying
another carrier is very slight.
Is There a Cure
At present there are no cures for any of the MPS diseases. Various experimental methods have been used to try
to replace the missing enzyme, but none so far have been of any significant long-term benefit. Bone marrow
transplants have been tried on MPS III patients, but with disappointing results.
How Does the Disease Progress
The disease will affect children differently, and its progress will be much faster in some individuals than in
others. Change will usually be very gradual, and therefore, easier to adjust to.
The disease tends to have three main stages:
1. During the child's pre-school years may be a very frustrating stage one for the parents. They begin to
worry as their child starts to lag behind their friends' children in development, and they may feel they
are being blamed for the child's overactive and difficult behavior.
The diagnosis is often made very late as some children do not look abnormal, and their symptoms are
among the most common seen in all children. The doctor has to be perceptive enough to recognize that
something serious is wrong and ask for urine and blood tests to help reach a diagnosis. It is not unusual
for families to have one or more affected children before the diagnosis is established.
2. The second phase of the disease is characterized by extremely active, restless and often very difficult
behavior. Some children sleep very little at night. Many will be into everything. Many like to chew;
hands, clothes or anything they can get hold of.
Sadly, language and understanding will gradually be lost and parents may find it hard not being able to
have a conversation with their child. Many will find other ways of communicating. Some children never
become toilet trained, and those who do will eventually lose the ability.
3. In the third phase of the disorder children with MPS III begin to slow down. They become unsteady on
their feet, tending to fall frequently as they walk or run. Eventually they lose the ability to walk. Life
may be more peaceful in some ways, but parents will need help with the physically tiring task of caring
for an immobile child or teenager.
Is Research Helping Today’s Families
Although there are currently no cures for MPS and related diseases, research is making great strides. Carrier
detection, the development of replacement enzymes, and the possibility of gene therapy, are among today’s
research themes and treatment options. Bone marrow transplantation has been considered successful for many,
though relatively few individuals qualify for this high-risk procedure. We’ve made major advancements in
research thanks to the fundraising efforts of the National MPS Society, its members, and friends.