Mucopolysaccharidosis VI (MPS VI)
MPS VI, also known as Maroteaux-Lamy syndrome, is caused by a deficiency of
an enzyme (arylsulfatase B) that is needed to break down the
mucopolysaccharide/glycosaminoglycan (GAG) dermatan sulfate, which is found in
many different parts of the body. GAGs are long, repeating chains of complex
sugar molecules. When the enzyme is absent, a progressive buildup of the GAG
material occurs in many of the tissues of the body and leads to many health
problems.
Forms of the disorder
As with the other forms of MPS, the symptoms of this condition are variable.
The frequency of Maroteaux-Lamy syndrome is estimated at 1 in every 215,000
births.
Clinical features
Individuals with Maroteaux-Lamy syndrome usually begin to display symptoms by
2 years of age. The symptoms may include short stature, an enlarged liver and
spleen, heart problems, joint stiffness, corneal clouding, coarse facial
features (flattened nose bridge, thick lips and an enlarged tongue), hernias,
“claw-like” hands, and hearing loss. Typically intelligence is not affected.
Genetics of the disorder
MPS VI is inherited as an autosomal recessive trait. Here's how that works:
All individuals have two copies of the specific MPS VI gene and usually both
function normally. However, children with MPS VI have alterations in both copies
of their genes so that neither gene copy works properly. Children receive one
copy of the altered gene from their mother and one copy of the altered gene from
their father. The parents are not affected with the condition because they have
one normal copy of the gene paired with one altered copy of the gene. The normal
gene produces enough of the specific enzyme to prevent the disorder. This is
referred to as being a carrier for the condition. When both parents are
carriers, they have a 25% chance with each pregnancy to have an affected child.
In turn, parents who are carriers have a 75% chance with each pregnancy to have
an unaffected child. More here
about autosomal recessive inheritance.
Treatment
Despite the fact that there is no cure for MPS VI, several therapies do exist
to treat the symptoms of the disorders. One method of treatment is enzyme replacement therapy
(ERT). Management of the disorder also involves symptomatic treatment of
specific complications that can arise in a patient with MPS VI.
Registry
The MPS VI Clinical Surveillance Program (CSP) is an ongoing, strictly
observational study that records the natural history and outcomes of patients
with MPS VI. There is no experimental intervention involved. The purpose of the
registry is to collect clinical information on a large number of patients
throughout the course of their lives. The registry is a way for healthcare
professionals to share information in a manner that respects patient
confidentiality, but at the same time contributes to a greater understanding of
the disorder and serves as a tool in the ongoing search for a cure for MPS
VI.