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Mucolipidosis Type IV (ML4)
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Description
Mucolipidosis type IV (ML4), first described in 1974, is the most
recently recognized Jewish genetic disease.
Mucolipidosis Type IV is an autosomal
recessive disorder, mainly seen in Jews of Eastern European background.
It is a cation channel disorder that is characterized by severe
neurological and ophthalmologic abnormalities. ML4 usually presents
during the first year of life with mental retardation, corneal
opacities, and delayed motor milestones. Children with ML4 typically
reach a maximum developmental age of 15 months in language and motor
function, although their receptive abilities are more advanced. Children
diagnosed with ML4 experience retinal degeneration that severely limits
their vision. There is currently no treatment for this tragic disorder.
Symptoms
Children with ML4 begin to exhibit
developmental delay during the first year of life. Many parents seek
ophthalmologic evaluations for pseudo-strabismus. Motor and mental
retardation ranges from mild to severe. The earliest sign is corneal
clouding; however, approximately 30% of patients develop clouding
between three and five years of age. Other eye findings may include
pseudostrabismus (false appearance of crossed eyes) and/or retinal
degeneration, which may lead to blindness in later years. There is no
gross involvement of the skeletal system nor urinary mucopolysaccharide
excretion. Patients currently range from one to 45 years of age.
Prognosis and life expectancy beyond the latter age is unknown.
Recently, a few very mildly affected children with ML4 have been
diagnosed. This raises the possibility of other undiagnosed mildly
involved patients.
The only way to know if your child has ML4
is to have your child examined and tested by a doctor.
As a parent, you can observe whether your child has the following
symptoms commonly associated with ML4 and generally appearing in the
first year:
· Pronounced developmental delays in gross motor skills, such as
sitting, standing and walking;
· Pronounced developmental delays in fine motor skills, such as holding
a cup or crayon;
· Pronounced developmental delays in speech;
· Vision problems of corneal clouding, retinal degeneration, sensitivity
to light, and strabismus; and,
· Low muscle tone (hypotonia).
If you
observe these symptoms, tell you child’s doctor.
Incidence and Carriers
One in 100 Ashkenazi Jews is a carrier.
The disease frequency is unknown.
The disease is transmitted through heredity. Both parents have to carry
the mutated gene for there to be a possibility of transmission to their
child.
If both are carriers:
· There is a One in Four chance that the child will
inherit the mutated gene from each parent and have the disease
· There is a One in Four chance that the child will
inherit normal genes from both parents and be completely free of the
disease.
· There is a Two in Four chance the child will
inherit one of a mutated gene from one parent and a normal gene from the
other parent, and in this case, be a carrier like the parents, but free
of the disease.
Treatment
At present, no specific therapy is available. Optimal supportive care,
including physical, occupational and speech therapy, can significantly improve
the function and quality of life of affected children. Families with
affected children should seek genetic counseling and be offered the option
of prenatal diagnosis for future pregnancies.
Testing
Diagnosis: The name,
ML4, derives from the presence of diagnostic storage bodies (cytoplasmic
inclusions seen under electron microscope) in almost every cell of these
patients. The storage bodies are similar to those observed in the
mucopolysaccharide and lipid storage diseases; thus the designation
mucolipidosis. The diagnosis should be considered in retarded Jewish
children who have corneal clouding. The electron microscopic
demonstration of characteristic storage bodies in a conjunctival biopsy
supports the clinical diagnosis.
There is a carrier screening
test
which requires a sample of blood that can determine whether or not there
is a gene mutation present for Mucolipidosis Type IV
Prenatal diagnosis for ML4 can be attained with the use of CVS (Chorionic
Villus Sampling) or Amniocentesis, which are performed early in the
pregnancy.
How can my child be tested?
There is now a simple blood test to
diagnose ML4. The blood test will also detect very low gastrin
(stomach acid) levels which are common in children with ML4.
Resources and More
National MPS Society, Inc.
17 Kraemer Street
Hicksville, New York 11801
(516) 931-6338
fax: (516) 822-2041
www.mpssociety.org
DNA Direct, Inc.
Pier 9 - Suite 105
San Francisco, CA 94111 USA
Phone: 415-646-0222
Fax: 415-646-0224
For Genetic Counseling and Screening
Resources – Click Here
Support Groups
Randy Yudenfriend
President, ML4 Foundation
MUCOLIPIDOSIS IV FOUNDATION
719 East 17th Street
Brooklyn, New York 11230
718-434-5067
Email: www@ml4.org
Website: http://www.ml4.org
National Mucopolysaccharidoses/Mucolipidoses Society (MPS), Inc
PO Box 736
Bangor ME 04402-0736
Phone: 207-947-1445
Fax: 207-990-3074
Email: info@mpssociety.org
www.mpssociety.org
Society for Mucopolysaccharide (MPS) Diseases
MPS House Repton Place White Lion Road
Amersham HP7 9LP
United Kingdom
Phone: 44 0845 389 9901
Email: mps@mpssociety.co.uk
www.mpssociety.co.uk
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