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What is MPS I? |
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MPS I (Mucopolysaccharidosis
I) is an inherited lysosomal storage disorder caused
by a deficiency of alpha-L-iduronidase, a lysosomal
enzyme normally required for the breakdown of certain
complex carbohydrates known as glycosaminoglycans
(GAGs). If the enzyme is not present in sufficient
quantities, the normal breakdown of GAGs is incomplete
or blocked. The cell is then unable to excrete the
carbohydrate residues and they accumulate in the lysosomes
of the cell. This accumulation disrupts the cell's
normal functioning and gives rise to the clinical
manifestations of the disease.
The incidence of MPS I is estimated to be at about 1 in 100,000 births. It is inherited in an autosomal recessive manner, affects males and females equally, and in most cases, both parents of an affected child are asymptomatic carriers of the disease.
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| Children diagnosed with MPS I have historically been classified into one of three categories based on the severity of their symptoms and rate of disease progression. It has now become clear, however, that there is a wide spectrum of severity in MPS I with much overlap between the categories. The following is a brief overview of the three categories of MPS I: |
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Hurler Syndrome: The most severe form of MPS I is characterized by progressive developmental delay and severe progressive physical problems. Death often occurs before 10 years of age. |
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Hurler-Scheie Syndrome: The intermediate form of MPS I is characterized by normal or near normal intelligence but more severe physical symptoms than those with Scheie Syndrome. |
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Scheie Syndrome: The attenuated form of MPS I is characterized by normal intelligence, usually normal height, and milder physical problems than Hurler-Scheie. These individuals potentially have a normal life span. |
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While patients with the most severe form of MPS
I are usually diagnosed by one to five years of age,
those with an intermediate or attenuated form of the
disorder may be under diagnosed. Over time, MPS I
patients typically get progressively worse, and experience
severe disabilities and possibly early death—factors
underscoring the importance of early diagnosis.
| The following are some of the features associated with MPS I: |
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Short stature |
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Macrocephaly (large head) |
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Coarse facial features |
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Progressively coarse facial features |
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Delayed or regressed mental development (the severe form) |
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Communicating hydrocephalus |
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Spinal cord compression |
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Carpal tunnel syndrome |
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Corneal clouding |
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Impaired vision |
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Recurrent otitis media |
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Impaired hearing |
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Recurrent sinopulmonary infections |
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Upper airway obstruction |
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Sleep apnea |
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Reduced pulmonary function |
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Cardiac abnormalities and valvular disease |
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Hepatosplenomegaly |
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Umbilical and inguinal hernias |
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Reduced joint range of motion |
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Dysostosis mutiplex (bone deformities) |
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Malaise and reduced endurance |
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Historically, treatment for MPS I has been limited
primarily to palliative care, care that addresses
the symptoms of the diseases such as respiratory
and cardiovascular complications, gastrointestinal
symptoms, skeletal manifestations, and loss of vision
and hearing. Today, in addition to palliative care,
there are other treatment options for consideration.
Enzyme replacement therapy (ERT) with Aldurazyme®
(laronidase) is designed to target the underlying
cause of the disorder by replacing the missing human
enzyme, alpha-L-iduronidase. Aldurazyme is approved
in the United States, European Union and additional
countries for the treatment of MPS I.* For additional
information about this therapy, please visit www.aldurazyme.com.
Additionally, bone marrow transplantation may be
a treatment option for the most severely affected
patients. Broad application of this therapy may
be limited by the risks associated with the procedure
and the difficulty finding an appropriate donor.
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For additional information about MPS I, please visit the following websites and others listed in the Resource Library:
www.MPSIdisease.com
www.MPSsociety.org The National MPS Society (United States)
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Important Safety Information |
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*Aldurazyme (larondiase) is
indicated for patients with Hurler and Hurler-Scheie
forms of MPS I and for patients with the Scheie
form who have moderate to severe symptoms. The risks
and benefits of treating mildly affected patients
with the Scheie form have not been established.
Aldurazyme has been shown to improve pulmonary function
and walking capacity. Aldurazyme has not been evaluated
for effects on central nervous system manifestations
of the disorder.
The most common adverse reactions associated with
Aldurazyme treatment in clinical studies were upper
respiratory tract infection, rash, and injection
site reaction. The most common adverse reactions
requiring intervention were infusion-related reactions,
including flushing, fever, headache, and rash. The
most serious adverse reaction reported with Aldurazyme
was an anaphylactic reaction, which occurred in
one patient approximately three hours after the
start of the infusion. The reaction consisted of
urticaria and airway obstruction. Resuscitation
required an emergency tracheostomy. This patient's
pre-existing MPS I-related upper airway obstruction
may have contributed to the severity of this reaction.
Approximately 91 percent of patients treated with
Aldurazyme were positive for antibodies to laronidase.
The clinical significance of antibodies to Aldurazyme
is not known. There are no known contraindications
to the use of Aldurazyme. Aldurazyme is available
by prescription only. For more information on Aldurazyme,
please see full prescribing information at www.aldurazyme.com.
Note: These website listings are provided by BioMarin
as additional information for patients, their families
and their healthcare providers. The web pages and
their content are maintained by the organizations
listed above. With the exception of its own website,
BioMarin does not endorse any particular organization
or the content contained on their website. |
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